A positioning instrument for buried non-metallic pipeline based on audio positioning method is designed. The positioning instrument is based on STM32F103C8T6 micro controller and consists of transmitter and receiver. Firstly, the working principle of the system is introduced, then the hardware circuit composition and control software design of transmitter and receiver are introduced in detail. The test results show that the positioning instrument is accurate and has strong anti-interference ability. The average detection rate is more than 80%, the highest horizontal accuracy is 0.2 m, the effective depth of detection is 1.8 m, and the effective length is 1000 m. It can meet the needs of urban construction excavation, water pipe leakage detection and other buried non-metallic pipeline positioning, and bring convenience for the management and maintenance of urban buried pipe network.