The tropical cyclone genesis potential index (GPI) that is currently used for seasonal forecast of tropical cyclone activity and the associated impact of global warming has been developed on the global scale without considering regional differences in tropical cyclone activity. Based on the best-track data from the Joint Typhoon Warning Center and NCEP/NCAR reanalysis data, this study focuses on the improvement of the GPI in the western North Pacific basin. In particular, the difference of tropical cyclone formation between the South China Sea and the western North Pacific is examined and taken into account in the new GPI. In the study, GPI is developed for the SCS (5-25 °N,100-120 °E) and the WNP (5-40 °N,120-180 °E), respectively. The improved GPI can simulate better the climate and interannual time scale spatial distribution than previous GPIs.