Abstract: In RF medium and high-power measurement system, the detector serves as a primary component of the medium and high microwave power meter. Its performance directly determines the measurement accuracy. To select an ideal detector with characteristics as broad dynamic range, superior linearity, and rapid response, this study investigates the linearity between the output voltage and input power of logarithmic and diode detectors at different frequencies. The experimental results indicate that during the whole power range, the logarithmic detector exhibits better power linearity than the diode detector within the specific frequency range. However, at both lower and higher frequencies, the logarithmic detector demonstrates significant nonlinearity, with irregular variations. In contrast, although the diode detector exhibits unsatisfying overall linearity, the fluctuation range of the output voltage is relatively small within the entire frequency range. It also demonstrates good performance stability, while the nonlinearity performance could be modelled and corrected. Hence, we formulate a nonlinear model for the diode detector, it can accurately and clearly reflect the nonlinear variation trends of the diode detector at different frequencies by using the piecewise fitting method, and the fitting effect is excellent, ensuring the accuracy of interpolation correction of the detector in the design and application of the microwave high-power meter.. This study provides a theoretical foundation for the optimization and frequency calibration of microwave high-power meters, offering valuable insights for improving the accuracy and reliability of medium and high-power measurements.