Hello everyone，
Sorry to disturb you. When I run ./regcm.x, "Floating exception" happens while runing for a moment. I tried to modify time step,ds , iy and ix, but they all didn't work. I really don't have  a way out. So I paste the regcm.in and domain.param as follows, everyone who knows please help me. 
Thank you very much! 
vi regcm.in：
***************************************
 $restartparam
 ifrest   =    .false.,
 idate0   = 1996111500,
 idate1   = 1996111500,
 idate2   = 1997030100,
 nslice  =        120,
 $
 $timeparam
 radfrq  =    30.,
 abemh   =    18.,
 abatm   =   300.,
 dt      =   150.,            #####120 、100 all don't work！
 ibdyfrq =          6,
 $
 $outparam
 ifsave  = .true. ,
   savfrq  =    48.,
 iftape  = .true. ,
   tapfrq  =     6.,
 ifrad   = .true. ,
   radisp  =     6.,
 ifbat   = .true. ,
 ifsub   = .true. ,
   batfrq  =     3.,
 ifprt   = .false.,
   prtfrq  =    12.,
   kxout   =          6,
   jxsex   =         40,
 iotyp   =          1,
 ibintyp =          1,
 ifchem  = .true. ,
chemfrq =     6.,
 $
 $physicsparam
 iboudy  =          5,
 ibltyp  =          1,
 icup    =          2,
   igcc    =          2,
 ipptls  =          1,
 iocnflx =          2,
 ipgf    =          1,
 lakemod =          0,
 ichem   =          0,
 $
 $subexparam
 ncld    =  3,
 qck1land = 0.00025,
 qck1oce  = 0.00025,
 cevap    = 1.0e-3,
 caccr    = 3.0,
 $
 $grellparam
 $
 $emanparam
 $
 $chemparam
 idirect   =    2,
 chtrname  =    'SO2',
 chtrsol   =  0.20,
 chtrdpv   = 0.00300,0.00800,
 dustbsiz  =  0.01, 1.00,
============================================================================================
vi domain.param ：
**********************
      parameter(iproj='LAMCON') ! Map projection (LAMCON,NORMER,POLSTR,ROTMER)
      parameter(iy=56)          ! number of grid points in y direction (i)
      parameter(jx=94)          ! number of grid points in x direction (j)
      parameter(kz=23)          ! number of vertical levels (14, 18 or 23)
      parameter(nsg=1)          ! number of subgrids in 1 grid (one direction)

      parameter(ds=45.0)        ! grid point separation in km
      parameter(ptop= 10.0)      ! pressure of model top in cb.

      parameter(clat= 33)    ! Central latitude (North positive)
      parameter(clon= 89)    ! Central longitude (East positive)

      parameter(plat=clat)      ! Pole latitude  (used for ROTMER)
      parameter(plon=clon)      ! Pole longitude (used for ROTMER)

      parameter(truelatL= 30.)  ! LAMCON true latitude (low  latitude side)
      parameter(truelatH= 60.)  ! LAMCON true latitude (high latitude side)

      parameter(ntypec=10)      ! Global topo/landuse data resolution (min)
      parameter(ntypec_s=10)    ! Global topo/landuse data resolution (min)
      parameter(h2opct=75.)     ! Minimum H2O percent to be considered water

      parameter(ifanal =.true.) ! Type of interpolation for topography
      parameter(smthbdy=.false.)! Smoothing of boundaries
      parameter(lakadj=.false.) ! Adjust Great Lakes levels (for US domain)

      parameter(igrads=1)       ! Output GrADS control file?
      parameter(ibigend=1)      ! 1=big-endian; (always 1)
      parameter(ibyte=4)        ! For direct access open statements (1 or 4)

 parameter(FUDGE_LND=.false.)   ! LANDUSE adjustments?
      parameter(FUDGE_LND_s=.false.) ! Subgrid LANDUSE adjustments?

      parameter(FUDGE_TEX=.false.)   ! TEXTURE adjustments?
      parameter(FUDGE_TEX_s=.false.) ! Subgrid TEXTURE adjustments?

      parameter(filout='../../Input/DOMAIN.INFO') ! Location/name of output
      parameter(filctl='../../Input/DOMAIN.CTL')  ! Location/name of GrADS ctl

c The following parameters can be reset later in RegCM/ICBC/icbc.param
      parameter(IDATE1=1996111500)   ! First date of simulation
      parameter(IDATE2=1997030100)   ! Last  date of simulation
              ! DATTYP : (ECMWF,ERA40,ERAHI,NNRP1,NNRP2,FVGCM,FNEST,EH5OM)
      parameter(DATTYP='ERA40')
              ! SSTTYP : (GISST,OISST,OI_WK,FV_RF,FV_A2,FV_B2,EH5RF,EH5A2)
      parameter(SSTTYP='OI_WK')
      parameter(LSMTYP='BATS')       ! LANDUSE legend (BATS or USGS)
      parameter(nveg=20)             ! Number of LANDUSE categories
                                     ! 20 for BATS, 25 for USGS.
      parameter(AERTYP='AER00D0')    ! AEROSOL TYPE option,
      parameter(ntex=17)             ! Number of SOIL TEXTURE categories
      parameter(NPROC=0)             ! Number of CPU used for parallel job.

=============================================================================