NECP-Atlas is a nuclear data processing code. It can read the evaluated nuclear data file (ENDF) and generate multigroup and continuous energy libraries for neutronics analysis and shielding calculation of the reactor. The code includes different code modules for different data procession functions: 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 constant, and so on. The NECP-Atlas code is tested against WIMSD Library Update Project (WLUP) benchmark, International Criticality Safety Benchmark Evaluation Project (ICSBEP) and some burnup benchmarks. The numerical results show that the NECP-Atlas code has comparable accuracy with NJOY-2016.