Climate change and climate events have significant impacts on the marine environment, and their impacts vary in time and space. The study looked at sea surface temperature (SST) in five large marine ecosystems (LME) in the northwest Pacific, including West Bering Sea, Sea of Okhotsk, Kuroshio, Oyashio, and the Sea of Japan, and the temporal and spatial trends of SST and their influences under the pacific decadal Oscillation (PDO) with El Niño and La Niña were analyzed. It was found that the SST of the other four large marine ecosystems, except the West Bering Sea, rose sharply around 1987, showing two changing patterns. After removing the long-term changing trend of SST, it was found that the SST of the five LMEs fluctuated up and down with time without regular periodic changes, but it was closely related to the El Niño and La Niña events. According to the spatial distribution of water temperature, the SST of each region showd a trend of increasing gradually from north to south, but the trend of increasing temperature was different. The SST of the whole region in West Bering Sea was increasing, and the cooling region was around Sakhalin and Hokkaido in Japan.