Food waste is considered a serious global societal problem. How to degrade of food waste in a green and effective way has been to a hot topic. In this work, a method with hot water extraction pretreatment of food waste was investigated and optimized. Under the optimal conditions, more than half of the solid food waste could be transferred to soluble sugars. Meanwhile, in order to improve the tolerance of Rhizopus arrhizus on the food waste hydrolysate, UV combined with chemical mutagenesis were carried out, and a mutant of Rhizopus RH-7-13-807 was obtained. With the mutant strain, the yield of fumaric acid fermented from food waste increased to 1.8 times compared with the original strain, and 23.94 g/L fumaric acid was obtained from the fermentation. Besides, the COD of food waste was evaluated for the degradation of food waste by the Rhizopus RH-7-13-807. The process would decrease the quantity of food waste to be disposed of, and benefit the environment.