Objective To provide data basis for improving the accuracy of food safety risk assessment in China， the cooking coefficients of five toxic metals in marine fish was studied.Methods Based on the consumption of 19 kinds of marine fish in Guangdong province， samples were divided into steamed， fried， roasted group and a control group （raw fish）. The concentrations of the total mercury， methyl mercury， arsenic， cadmium and lead were determined before and after the cooking process， and the cooking coefficients of five toxic metals were calculated.Results The concentrations of total mercury， methyl mercury， total arsenic and cadmium in fried and roasted fish were significantly higher than those in control group （P<0.05）， while the concentrations of lead in steamed fish were significantly lower than those in control group （P<0.05）. In addition， the cooking coefficients of heavy metals in different kinds of marine fish were different under the same cooking method， and the coefficients of heavy metals in the fried and roasted group were higher than those in the steamed group.Conclusion The concentrations of total mercury， methyl mercury， total arsenic， cadmium and lead in marine fish can change significantly after cooking. During risk assessment， appropriate processing factors should be selected to improve the accuracy of risk assessment in combination with the needs of the assessment situation.