Objective To develop an instrument that detects the behavior of mice in tail suspension during pharmaceutical experiments. Methods One pair of infrared sensors was used for signal conversion. A diode laser was used for positioning. A 51-series microcontroller was used to control the experimental setup and record the results. Results A microcontroller-based experimental instrument that can automatically detect the behavior of animals in tail suspension during pharmaceutical experiments was developed. ConclusionsOur experimental results with 30 mice indicate that the developed instrument provides an innovative tool for detecting the behavior of animals in tail suspension.