Abstract: Based on the analysis data of 52 samples for cadmium content of both total and each state in bottom mud of shallow sea of the Northern Liaodong Bay, the distribution characteristics of cadmium in different existing states are researched. The environmental factors and ecologic effect of the cadmium in bottom mud are also studied. The result indicates that the cadmium content in bottom mud is relatively high. The cadmium content of non-residual state, mainly ion-exchange state and carbonate-binding state, is very high, accounting for 90% of the total. There is a notable correlation between the total content and each states of cadmium, with consistent distribution characteristics. The samples with highest content are concentrated at Jinzhou Bay. Each state of cadmium in bottom mud is notably correlated with the organic matter in bottom mud and the cadmium in sea water.