The stable isotope variation in spring and summer precipitation of Sichuan and Guanzhong basin are computed and analyzed by using isotopic data of Chengdu and Xi'an station of Global Network of Isotope in Precipitation(GNIP).The results show that a significant seasonal δ¹⁸O variation in precipitation exists in both the two basins.Correlation analysis indicates that neither the temperature effect nor the amount effect is pronounced for precipitation δ¹⁸O variation in spring and summer.The Local Meteoric Water Line(LWML) and its gradient and increment reflect the local climate characterstics as well as rainfall vapor source.Thus,the rainfall vapor source is considered to be the main factor influencing the δ¹⁸O variation in precipitation of the two basins,and local vapor transport pathway affected by geographical factors determines the stable isotope composition.