Hi Zhoujun, The operation of converting an NcML file (or any CDM dataset) to a NetCDF-4 file is something that can be done from the command-line [1]. If you would like to do it programmatically, I suggest just following the lead of the ucar.nc2.write.Nccopy.main() method [2], which is what is being invoked when converting from the command-line. Cheers, Christian [1] http://www.unidata.ucar.edu/software/thredds/current/netcdf-java/reference/manPages.html#nccopy [2] https://github.com/Unidata/thredds/blob/v4.6.3/cdm/src/main/java/ucar/nc2/write/Nccopy.java#L126 Ticket Details =================== Ticket ID: QJL-517256 Department: Support netCDF Java Priority: Normal Status: Closed