The scandal of melamine-adulterated infant formula in China in September 2008 demanded the need to assess the extent of melamine contamination in the environment and food products and possible risks of consuming melamine-contaminated diets. In this work, our extensive work tested water, soil and crop samples from 21 provinces in China. Soils nearby and waste waters from melamine-manufacturing factories were examined, and the highest melamine concentrations in waste water and soil samples were 226.766 and 41.136mg/kg, respectively. Six of 94 irrigation water samples had melamine at a concentration of 21–198μg/L. Only 1 sample collected from 124 farmlands farther than 150km from melamine factories was detected for melamine at a content of 176μg/L. Only 3 out of 557 crop samples contaminated more than 1mg/kg melamine, with the highest level of 2.05mg/kg in a wheat sample. When basal diets contained 2mg/kg melamine were fed to various animals, deposition of melamine in animal tissues and products was all lower than 122μg/kg. The melamine deposition was much higher (e.g., 4483μg/kg in the kidney of chicken) when diets contained 100mg/kg melamine but was found to be completely depleted after 96h for all animals after switching to the basal diets. Our work may be valuable to regulate melamine production and monitor the safety of food and animal products.