The invention discloses a pretreatment and beneficiation method of low-grade refractory molybdenum ore. The pretreatment and beneficiation method comprises a raw material pretreatment and beneficiation process and specifically comprises the steps that after being crushed to be smaller than 2 mm, the low-grade refractory molybdenum ore is heated through a microwave heating device and pretreated through a water quenching method, then the pretreated low-grade molybdenum ore is ground, a collecting agent and a regulator are added for flotation, and final high-grade molybdenum concentrate products are obtained. According to the pretreatment and beneficiation method, the process is simple, the ore grinding cost of the low-grade molybdenum ore can be reduced, the separation index can be increased, and no pollution is generated to the environment.