Aiming at the problem that it is difficult to accurately measure the high rotational speed of high rotation ammunition, a speed measuring device based on geomagnetic sensor is designed. The measurement device mainly uses HMC1053 three-axis geomagnetic sensor and STM32H753 ARM chip to complete the speed measurement function. According to the characteristics of the output signal of the geomagnetic sensor, the time-domain characteristics of the rotational speed signal are simulated and analyzed by using the zero-crossing detection method, and the time-frequency characteristics of the rotational speed information are also simulated and analyzed by using the short-time Fourier transform and continuous wavelet transform methods. The results show that the continuous wavelet transform method has higher frequency resolution and higher rotational speed precision. Finally, the machine speed test and missile-borne flight test are carried out to verify that the maximum error of the machine speed test is 0.011 3 r/s. The test results show that the speed measurement method is feasible, which provides relevant support for the navigation and guidance technology of high rotation ammunition and has certain engineering application value.