Abstract: In the areas such as Japan and eastern and middle part of China,the performance augmentations of QZSS to GPS on navigation precision,availability and integrity are simulated and compared.The results show that QZSS consist of only three satellites can provide effective augmentation to GPS in above fields.With the mask angle increasing,the performance improvements will become more obvious.The results also show that QZSS can effectively reduce the performance deterioration of GPS in the wartime,because of results from the invalidation of part satellites.The analysis results can be used as guidance for the effective application of GNSS resources in Chinese middle part and eastern key area.