The risk caused by microbiological hazards in food is very concerned to human health.Codex Alimentarius Commission(CAC) has constructed a framework on conducting microbial risk assesment,which involves four main steps:Hazard Identification,Hazard Characterization,Exposure Assessment and Risk Characterization.Risk assessment applied to microbial food safety is a scientifically based methodology to estimate the probability and severity of a health disturbance as a consequence of consumption of food contaminated by microorganism or microbial toxins.Each step of the framework and the related influence factors were summarized in the article.