Our study aims to design and apply a digital physics experimental system based on millimeter wave radar, specifically for the precise quantification of spring harmonic motion. Traditional physics experiments are often limited by errors from manual measurements and visual observation, but this system uses a 24 GHz millimeter-wave radar combined with a custom-designed circuit board for real-time, non-contact motion measurement. By designing the printed circuit board, writing firmware to convert analog signals into digital data, and using Python for data analysis, the system successfully measured the effects of different masses on the spring's oscillation frequency. The experimental results showed that after accounting for the spring's own mass, the root mean square error between the measured data and theoretical values decreased from 0.62Hz to 0.35Hz, demonstrating the system’s high accuracy. Additionally, the stability of the radar module in non-contact measurements highlights its potential applications. This study successfully addressed measurement errors in traditional physics experiments, enabling precise observation of motion using millimeter-wave radar technology. Furthermore, the open-source design of this system will help promote its use in more school physics labs, providing students with advanced experimental tools and data analysis experience. The study showcases the potential of millimeter-wave radar technology in physics experiments and offers an efficient and low-cost solution for future teaching experiments.