Abstract: A home-developed nuclear data processing code named as NECP-Atlas was described in this paper, which included different code modules for different data procession functions. This code can generate WIMS-D or WIMS-E format multigroup library from evaluated nuclear data file, through reconstruction of resolved resonance cross section and linearization of cross sections, Doppler broadening, calculation of unresolved resonance cross sections, calculation of thermal neutron scattering cross sections, calculation of multigroup cross section, and so on. The NECP-Atlas code was tested against WIMSD library update project (WLUP) benchmark and international criticality safety benchmark evaluation project (ICSBEP). The numerical results show that the NECP-Atlas code can get results comparable with NJOY-2016 code.