Objective To evaluate the excess cancer risk of semiearbazide(SEM) from the breakdown of azoformamide (ADA) as the flour treatment agent added in bread flour at the maximum usage level. Methods The concentration range of SEM in bread was estimated from the maximum usage level of ADA in wheat flour and the decomposition rate of ADA in the baking process. The time weighted lifetime average daily exposure levels were calculated based on the estimated SEM concentration range and the bread consumption data from Chinese nutrition and health survey. Extra cancer risk was calculated using linear extrapolation model based on the data from experimental animal carcinogenic experiments. Results When ADA was added in bread flour at 45 mg/kg, SEM from bread theoretically increased the extra lifetime cancer risk in the range of 1.31×10-7-1.97×10-6for consumers with average bread consumption; for the high consumption (P97.5) consumers, the SEM exposure from bread theoretically increased the lifetime cancer risk of in the range of 4.09×10-7-6.14×10-6. Based on the time-weighted daily exposure level, the extra cancer risk of SEM for different age group was within the range of 10-9-10-6. Conclusion SEM from the breakdown of ADA added in bread flour at the maximum usage level poses acceptable risk to the consumers. Thus, the current maximum usage level of ADA in the standards for use of food additives (GB 2760-2014) can effectively protect the consumers in China.