Abstract: Multi-functional lattice code SONG is now being developed, to meet the research demand of new type reactors. So it is necessary to consider the new specifications on these reactor in fuel, structure, coolant, modulator, spectrum and depletion depth, in building the new multi-group cross section library. In the presence of these new characteristics, the library is specially designed in dealing with burp-up chain, energy structure, reaction path, resonance parameters and so on. Using the Evaluated Nuclear Data File（ENDF）, the nuclide date processing code（NJOY）, nuclide date auxiliary processing code（RUNBAT） and library management code（MANLIB）, the multi-group cross section library is built. With this library, a series of verification work is preliminarily carried out. The calculated results show that the library is reliable and meets the requirement of lattice code