"Big data" "Internet Plus" and information technology have become important means to promote environmental governance systems and governance capacity modernization. An objective requirement of the development of China's environmental information and rational choice is to further promote "Internet Plus" smart environmental protection construction. However, China has not yet formed a suitable "Internet Plus" smart environmental protection assessment index system with which the environmental information construction investment (cost) and production efficiency (output and benefit) could be evaluated by an objective, fair, and accurate method. Based on the analysis of the overall structure and the target of "Internet Plus" smart environmental protection, following the principles of representativeness, independence, comprehensibility, collectability, and extensibility, using the method of factor analysis, literature research, and expert consultation, an assessment index system including four dimensions, 14 factors, and 64 indexes were formed. The introduction of the assessment index system should be of great significance in the guidance of the orderly development of "Internet Plus" smart environmental protection construction and in the promotion of the development of environmental protection information.