Abstract: Cryptodestes ferrugineus (Stephens) is one of the world's stored grain pest and one of the main stored grain pests in China. At present, phosphine fumigation is the most commonly used method for the prevention and control of C. ferrugineus. In recent years, the resistance of C. ferrugineus against phosphine has become more and more serious. This problem has become the most difficult challenge for application phosphine and pest control in stored grain. In order to effectively prevent and control the damage caused by C. ferrugineus in grain storage, it is of great significance and urgent to study the resistance management methods for pest control. In this paper, the effects of prolonging the fumigation time of phosphine and three protective agents on the control of C. ferrugineus resistant to phosphine were studied. The resistance level of the adult of C. ferrugineus against phosphine was measured by FAO method, the toxicity of pirimiphos-methyl, malathion and deltamethrim-pirimipins-methyl against adults of C. ferrugineus was determined by filter paper method. Contact killing effect of pyrimidine methyl on the adult of C. ferrugineus was evaluated. The results showed that prolonging the fumigation time of phosphine had a significant insecticidal effect on C. ferrugineus. When the concentration of phosphine was 1.38 mg/L, after the fumigation time for 2, 3, 4, 5, 6 and 7 days, the mortality rate was less than 50% in 2 to 5 days, 76% in 6 days and 94% in 7 days, and the mortality rate increased with the fumigant time significantly. When the concentration of phosphine was 13.8 mg/L for 20 h, the survival rate of C. ferrugineus was 98%. The results indicated that C. ferrugineus showed extremely high phosphine resistance, and it was more feasible to prolong the fumigation time of phosphine than to increase the concentration of phosphine. The LD₅₀ of three kinds of grain protectant pirimiphos-methyl, malathion and deltamethrim-pirimipins-methyl for 24 hours were 7.519, 26.914 and 6.071 μg/cm², respectively. The LD₅₀ for 48 hours were 5.031, 19.401 and 3.796 μg/cm², respectively. After 72 hours treatment, the LD₅₀ were 3.438, 13.646 and 2.936 μg/cm², respectively. These results indicated that among the three grain protectants, pirimiphos-methyl and deltamethrim-pirimipins-methyl had better effect than malathion. The mortality rate of C. ferrugineus reached 100% after being treated with pirimiphos-methyl 6 μg/cm² for 48 hours and 10 μg/cm² for 10 hours. The results showed that prolonging the treatment time and increasing the dosage of the grain protectant significantly increased the mortality rate of C. ferrugineus. Therefore, the dosage of protective agent can be appropriately reduced or the treatment time can be prolonged, which can not only achieve the pest control effect but also delay the development of resistance.