Abstract: The harmonic RF tag with semiconductor devices is an important part of harmonic radar system. Efficient and miniaturized tags are conducive to increasing the working distance of harmonic radar and expanding the application scenarios of harmonic radar. To solve the problem of the accuracy of the device equivalent model when the device metal-semiconductor junction voltage is not at zero bias, this paper proposes an improved dynamic equivalent model based on the change rule of the junction capacitance with the junction voltage, and uses the tag implementation method of combining the dipole antenna with the printed nonlinear circuit. Simulation and measurement analysis show that the echo signal strength of the new tag in the target frequency band has increased by about 10 dB compared to the original tag, and the antenna length has been shortened by about 23%, achieving the design goal of efficient miniaturization. It can be seen that the dynamic equivalent model provides accurate guidance for the selection and design optimization of harmonic radar tag devices.