Based on the general ecosystem protoplast and results of analysis of the contents of 2607 fish individuals belonging to 53 species in the Jiaozhou Bay ecosystem, the ecosystem is dividied into six subsystems: zoophankton X2, benthos X7，detritus feeder X4，zooplankton feeder X3，zoobenthos feeders X8 and nekton feeders X5， plankton X1, and the content of organic matter in sediment X6 were regarded as input and the nekton feeders as output, over the year mooth by month investigation data was used to develop the ecosystem model by applying grey system theory, whose differential equations are as follows: