Based on reanalysis data and numerical simulation, the meteorological characteristics of the lower circulation over western North Pacific and the seasonal differences in correlations between them and sea surface temperature (SST) anomalies are analyzed. The results are summarized as follows. 1) The spatial scale and the location of the anomalous anticyclone/cyclone over western North Pacific are different in spring and summer. From spring to summer, the anomalous circulation shrinks in spatial scale and its center shifts towards the northwest. 2) There are seasonal differences in the interactions between low-level circulation and local SST over western North Pacific. In spring, cold SST interacts with the upper-level anticyclone over western North Pacific; whereas in summer the influence of the atmosphere on the ocean dominates and anomalous anticyclone/cyclone can heat/cool the SST with a time lead of 3-4 days. 3) The maintenance of anomalous western North Pacific anticyclone (WNPAC) in summer is mainly attributed to the forcing of nonlocal SST (the North Indian Ocean warming and central Pacific cooling). The influences of the two factors on WNPAC also has seasonal differences. The North Indian Ocean SSTs mainly act from May to July, while the central Pacific SSTs act mainly in late summer.