Abstract: In this paper, we propose and experimentally study a scheme for generating tunable microwave frequency combs based on optical injection into a vertical cavity surface emitting laser (VCSEL). The scheme employs a novel VCSEL as the pump laser. The experimental setup and working principle are first introduced, and then the influence of the injection light power, RF signal modulation frequency, modulation amplitude, and modulation DC bias voltage of the master laser on the bandwidth, the peak maximum power, and the flatness of the generated microwave frequency comb signal are studied experimentally. The results show that by selecting appropriate parameters, a microwave frequency comb signal with a bandwidth of 10.51 GHz, a peak maximum power of −45.89 dBm, and 24 comb lines can be obtained. The experimental results of this paper can show reference for optimizing the microwave frequency comb system and the practical application of microwave frequency comb.