The melamine incident 2008 was a global food crisis and drew attentions to other potential food safety risks. Although there are regulations and standards for food safety, but one common problem in food risk management is that it lacks on hazard indicators - indicators in ranking of food risk and control. The three algorithms developed in this article were: 1. A distribution fitting algorithm proposed to estimate population parameters for left-censored melamine data under log-normal assumption. 2. A risk index algorithm proposed to screen out food product categories with higher concentration without considering measurement uncertainty. 3. A misjudgment probability algorithm proposed to calculate the probability that food categories containing melamine more than legal limit but classified satisfactory under consideration of measurement uncertainty. The test results on melamine collected from the website of the Centre for Food Safety of Hong Kong are empirically analyzed by the proposed algorithms. The risk index (RI) and the consumer¡¦s risk (CR) of multiple food categories are discussed and compared in details. Based on risk index (RI) and consumer¡¦s risk (CR), we build a risk assessment process to help assess melamine risk and make sample strategy in surveillance programme. The proposed risk assessment process can be applied to other chemical contaminant problems such as plasticizer (phthalate esters) and ractopamine (paylean), etc.