Abstract: Objectives The present study was conducted to evaluate the tendency of infections diseases in Hangzhou in 90's．Methods The incidence rate of infectious diseases was calculated annuany．Linear regression analysis method was apphed to analyze the incidence and its tendencyas well as its endemic mode in Hangzhou in 90's in terms of 3 statistic indexes，I．E．Average increasing rate，annual change percentage and annual change contribution ratio．Results The incidence rate of syphilis rose fastest，and that of pertussis declined fastest．As for those major infectious diseases，the incidence rates of hepatitis and dysentery were in a shfirddng tendency while these of blannorrhea and phymatinsis were in an increasing tendency The differences of annual change percentage for the six diseases，pertussis，hemoffhage fever hepatitis，syphilis，blennorrhea and typhoid were all significant，yet it should be paid attention that the difference of annual changing percentage for dysentery was not significant According to the calculated annual change contribution ratio，hepatitis contributed the most to the decline of the incidence rate．Whereas biennorrhea contributed the most to the increase．During the ten years，the incidence rates of infections disease had been changing annually and were statistically significant Conclusion The incidence rate of infectious diseases showed a tendency of obvious decline，which meant that the application of prevention and control measurements took positive effect