The existing PWR NPP reload core loading pattern optimization techniques and their features are introduced briefly. System framework based on genetic algorithms for PWR NPP low-leakage reload core loading pattern search technique is established. The multi-chromosome encoding and decoding, fitness function, genetic operation and decoding techniques for the study are designed. The developed optimal program using C language and its test results show that the technique is feasible and effective. Application results demonstrated that the optimized reload loading pattern for reload core can be obtained by using this system.