Frequency is the most fundamental parameter of microwaves. Due to the extremely short pulse width of high-power microwaves (HPM), their frequency measurement requires special methods that differ from conventional microwave frequency measurement techniques. Currently, common HPM frequency measurement methods include the waveguide dispersive line method, frequency mixing method, filtering method, cutoff waveguide method, and direct reading method using oscilloscope. Additionally, some researchers have proposed approaches such as the evanescent mode attenuator measurement method. This chapter provides a detailed introduction to the principles and procedures of each of these measurement methods.