Abstract: Objective To investigate the prevalence of category A and B infectious diseases in Daishan county, Zhejiang province from 1956 to 2009, providing the basis for development of prevention and control measures. Methods Descriptive epidemiological approaches were employed to analyze the epidemic data of category A and B infectious diseases in Daishan from 1956 to 2009. Results From 1956 to 2009, Daishan witnessed decreasing average morbidity and mortality rates of category A and B infectious diseases. In the 1950s and 60s, the predominant morbidity was respiratory diseases, which changed to vector-borne and natural-focus diseases in the 70s. As for the 80s and 90s, intestinal infectious diseases were mostly prevalent, whereas blood and sexually transmitted diseases leaped sharply and became the major kinds of disease after 2000. Immune-related, vector-borne and nature-focus diseases had been effectively controlled or eliminated. Conclusion With declining morbidity and mortality of infectious diseases in Daishan over the six decades, the infectious disease spectrum has fundamentally changed. Currently, blood and sexually transmitted diseases are predominant, and thus corresponding preventive and control measures should be carried out immediately.