Abstract: Using the NCEP/NCAR reanalysis dataset, the Hadley sea surface temperature (SST) data and the western Pacific Subtropical High (WPSH) indexes provided by the National Climate Center (NCC) of China, different impacts of Indian Ocean (IO) SST anomalies (SSTA) dependent and independent of ENSO on the variation of summertime WPSH are investigated. It is demonstrated that when the preceding El Niño signal is removed from the SSTA, SST is warmer than normal in the IO but cooler in the Maritime Continent (MC) in the summer. An anomalous anticyclonic circulation appears to the northwest of the cold SSTA center. At the same time, warm IO SSTA trigger Kelvin waves that mainly affect the region west of the MC. The abnormal atmospheric circulations are roughly symmetrical about the equator in the western Pacific. Meanwhile, the abnormal cooling over the South China Sea and the northwestern Pacific caused by less latent heat release leads to the intensification and southwestward expansion of the WPSH. However, in the context of early El Niño, warm SSTA appear over both the IO and MC, resulting in stronger eastward propagation of Kelvin waves and enhanced circulation anomalies north of the equator. The diabatic cooling and the Ekman pumping generate abnormal negative vorticity in the lower troposphere, which is favorable for the intensification and southwestward expansion of the WPSH. Moreover, in the background of ENSO condition, the WPSH is forced to vary by remote IO SSTA, which actually include both the lagging effects of signals with a short period of 3-7 years from the central-east Pacific and simultaneous impacts of local SSTA with 2 year and 8 year periodic oscillations from the tropical India Ocean. These results are helpful for better understanding and predicting variations of the WPSH.