In recent years, the rapid development of heavy industry has exacerbated the deterioration of air quality, and environmental governance has become increasingly important. However, most of the existing air quality assessment systems at home and abroad have single forms, low accuracy and limited assessment ranges. In other words, they cannot accurately display the air quality situation in a diversified way. This study develops an air quality assessment system which integrates data collection, standardized processing and air quality assessment. The system has the following advantages. It obtains data from air quality monitoring websites with Web crawlers and enables data extraction, data cleaning, data unit conversion, pollutant classification and data processing with a variety of standardization methods to ensure the accuracy of air quality assessment. It has numerous assessment modes, involving the assessment by hour, day, month, monitoring station location and pollutant type, which addresses the single forms and inaccurate assessment of most air quality assessment systems. It can provide real-time air quality information for users and accurate data preprocessing results for researchers. With stable and reliable operation, friendly interface and rich functions, the system can meet the need for comprehensive air information management and evaluation.