In this paper, the lake ecosystem health evaluation index system was established using the frequency analysis method. Then, the weights of the index were calculated by the Combination Assigning Method combined Variation Coefficient Method with the Information Entropy Weight Method. Finally, the evaluation method of the lake ecosystem health was proposed based on the coordinated development degree of ecological-social service function. In addition, the classification standard of the lake ecosystem health level was given out from the aspects of lake comprehensive development level and lake coordinated development degree. Based on this evaluation method, Lake Baiyangdian ecosystem was used as the research object to carry out the empirical study on the health status and the coordinated development degree. The results show that the comprehensive development level of Lake Baiyangdian ecosystem is in the state of unhealthy morbid state, and the coordinated development degree belongs to the critical coordinated development. This method takes the coordination and development of ecological integrity and social service function into consideration while evaluating lake health, and provides suggestions for lake management construction from the point view of coordination and development.