In order to avoid the error of measuring the parameters of plastic pipes in the construction of hard plastic pipes, a measuring system for detecting the movement of steel beads in pipes is designed. The hardware of the system is controlled by STM32F103 single chip microcomputer, and the key measurement module is ExEX-2E1-Z metal sensor and SCA61T-FA1H1G inclination sensor. The system software mainly uses KEIL 5 software to compile the STM32F103 single-chip microcomputer, in order to drive the metal sensor and inclination sensor to measure and analyze the data, get the movement of the steel ball, and display the measurement results of the movement of the steel ball through the color LCD module. In the measurement method, the least square method is used to establish the calculation model of inclination angle, and curve fitting is carried out to achieve angle measurement. The overall function of the system is to measure the number, direction, period and angle of steel balls in non-transparent hard plastic pipes without machining marks.