Abstract: There has been increasing research interest in the Changjiang River Estuary since it was discovered to be hypoxic in the 1950s. However, long-term continuous monitoring of the area remains limited, which has in turn affected the understanding of dynamic hypoxia in the estuary. This study used monitored bottom dissolved oxygen (DO) data for the southwest Changjiang River Estuary from January to May, 2020 to identify the key factors affecting spring hypoxia. Of the two hypoxia events that occurred during the observation period, the first was relatively slow, whereas the second was faster. The first hypoxia event occurred from January to April during which DO slowly decreased and then stabilized in April. The second hypoxia event occurred during the middle and late May during which DO rapidly decreased from near DO saturation to hypoxia within 10 days. Correlation analysis showed that the first event could be attributed to sediment oxygen respiration during decomposition of organisms, in which stratification due to weak wind conditions maintained hypoxia. The onset of strong winds in early May ended the stratification, effectively ending the hypoxia event. Mixing resulted in bottom nutrients being transported to the surface layer, resulting in a phytoplankton bloom. The second rapid hypoxia event at the end of May could be related to the large biomass of dead phytoplankton settling on the seabed at the end of the phytoplankton bloom and the consequent decomposition process. By using continuous observation data, the analysis of two consecutive hypoxia events in spring 2020 can supplement the understanding of seasonal changes of hypoxia at the Changjiang River Estuary, and provide important references for studying the variation characteristics and formation mechanism of spring hypoxia.