Abstract: Based on the monitoring data in August in the North Yellow Sea section from 1976 to 2015, spatio-temporal modes on the inter-annual variation of DO and Apparent Oxygen Utilization (AOU) in summer in the North Yellow Sea section were studied with the analysis methods of Rotated Empirical Orthogonal Function (REOF) and so on. The results show that the inter-annual variation change of DO and AOU can be divided into 3 spatio-temporal modes, respectively. The first and the second mode are the main influencing components of the inter-annual variation of hypoxia and oxygen poor in near bottom layer. The third mode was the main influencing component of high and rich oxygen in mixing layer. The production and consumption of oxygen from biological active components (BAC), the process of increasing and decreasing oxygen in the ocean current transportation is the main factors affecting the inter-annual variation of DO and AOU in summer, the inter-annual variation of thermocline intensity is not the main factor. Since 2001, the inter-annual variation of monthly air sea O₂ flux in the surface layer has changed from oxygen sink to oxygen source, the increase of dissolved oxygen content and production of oxygen from biological active components (BAC) in the surface layer is main reasons for the reverse. The similarity is low between the mean annual DO and AOU distribution in the North Yellow Sea. The mean annual temperature, salinity and sediment oxygen demand, wind driven circulation are the main factors affecting the mean annual DO and AOU distribution. The oxygen consumption process of BAC is a main influence factor of the monthly mean DO and AOU in each layer in summer and the monthly mean temperature change is a secondary factor. Compared with the data 3 decades earlier, the spatial distribution and temporal pattern of the seasonal variation of DO and AOU filed in Yellow Sea have changed due to the linearly increase in the amplitude of hypoxia and hypoxia areas.