Abstract: Objective The present study was conducted to get the knowledge of the factors influ-encing the reporting of notifiable diseases by medical institutions after applying direct reporting net-work system and provide scientific basis for further improving the reporting level and quality of no-tifiable diseases of medical institutions．Methods Stratified random sampling was adopted to survey the operation status of direct reporting network system in medical institutions．Which participated in direct reporting network system in 2004．And CHAID (Chi-squared Automatic Interaction Detector) was adopted to explore possible influence factors of reporting communicable diseases by medical institutions．Results 671 institutions were surveyed and averagely there were 306 cards of conmmu-nicable diseases were reported every year．The response rate and qualified rate of questionnaire were 89.3％ and 97.5％ respectively．Through CHAID model．9 factors that influence medical institutions to report communicable disease by were found：1) the grade of medical institutions,2) the number of staffs responsible for managing of epidemic status，3) the situation of full-time personnel，4) the status of personnel with college degree，5) property of medical institutions,6) fixed number of year of starting to report，7)latitude of receiving reporting card,8) daily times of receiving cards,9) per capita years in managing epidemic StatuS．Medical institutions at different levels were affected by different factors．Conclusion Medical institutions at province，city and county levels should in-crease the number of full-time professional staffs and the times of collecting cards，pay great atten-tion to epidemic status report and managing all items of principles．Medical institutions at factories．Mines，country and other levels should improve the quality of reporting communicable diseases through improving the capacity of the personnels responsible for managing epidemic status and mak- ing card collection and report system available，etc．