In the Low Earth Orbit(LEO) scenario, beam hopping technology can flexibly allocate system resources and is suitable for the scenario of uneven service distribution. Time Division Duplex (TDD) mode has low requirements on the terminal and is conducive to the development of upstream and downstream asymmetric services. Therefore, a resource allocation algorithm is proposed for low-orbit satellite beam hopping based on TDD. Firstly, the resource allocation model of LEO reverse link supporting beam hopping and Multifrequency-Time Division Multiple Access(MF-TDMA) is established to minimize the time domain resource consumption in condition of satisfying the service requirements. Secondly, considering the dynamic time-delay compensation of satellite and earth, a multi-level beam hopping time slot architecture design is adopted to maximize the available time slot. The upstream and downstream time slot switching model is established, and a beam hopping time slot scheduling optimization method is proposed based on TDD. Simulation results show that compared with traditional MF-TDMA resource allocation method or fixed multi-beam splitting algorithm, the proposed algorithm can effectively improve the time slot utilization and throughput of the system.