Abstract: Objective This study was conducted to understand the distribution and change of leptospira bacteria among people and host animals in Zhejiang Province，and therefore provide scientific evidence for study of the epidemic rule of leptospirosis，as well as formulation of prevention and control measures．Methods The Microscope Agglutination Test (MAT)was applied to antibody determination for serum of clinically diagnosed patients and host animals，and the kidneys of rat，frog，pig，and teal，as well as midstream urine of cattle，were collected for isolation and culture of pathogen．Results In recent years，the bacteria floras corresponding to serum antibody of patients were mainly of icterohemorrhage and hebdomadis，which had not changed significantly as compared with that from 1990 to 2000．The autumn leptospira bacteria increased apparently in proportion when compared with that from 1999 to 2000，which became the main flora．The main bacteria flora corresponding to positive serum antibody of host animals was of autumn．Conclusion The leptospira bacteria carried by host animals had been changed，and the situation was not completely identical to that of bacteria flora carried by patients，which had been serologically defined．The prevention and control of leptospirosis in Zhejiang Province cannot be ignored，and especially，the monitoring of host animals should be strengthened．