In this paper, a design of air pollutant monitoring system with six modules based on Semi-supervised learning (SSL) is designed. More specifically, the data acquisition module, data pre-processing module, data classifier module, comprehensive analysis module, auxiliary sorting module, computer terminal module respectively realize data collection, dimension reduction pre-processing, classification, comprehensive analysis, sorting, observation and monitoring. After system operation, it perfectly realized the real-time monitoring and timely warning of haze pollution, and provided data support for the precision of urban air pollution prevention. The application of modern science and technology in air pollution monitoring has been realized, and the ability and level of air pollution prevention and control supervision have been improved. The experimental results show that the proposed system has higher accuracy monitoring of classification.