Abstract: The NECP code package is a deterministic nuclear reactor physics code system developed by the Reactor Physics Team of Xi’an Jiaotong University. The NECP code package includes NECP-Atlas, Bamboo, X and SARAX codes. The code package was verified and validated by a large number of benchmarks and evaluated experiments. The numerical results show that the NECP code package has high precision and can meet the physics calculation requirements of different reactors. It has wide generality and realizes high fidelity modeling and simulation of pressurized water reactor. At present, the NECP code package was applied to several key projects such as large-scale pressurized water reactor project and demonstration fast reactor project in China. The application results show that the NECP code package reaches or even surpasses the level of other nuclear design codes abroad, and has great significance in Chinese code autonomy of nuclear power and improvement of nuclear design capability.