As the industrial basic part，the gears machining accuracy has a significant impact on the overall accuracy and reliability. It is one of the important factors that determine the quality of our country's manufacturing industry. In order to improve the detection accuracy and detection speed of gears, a gear lead precision detection method based on laser ranging is proposed. And the gear lead detection system is also developed on the basis of this method. Because of the laser measuring advantages in terms of metal and reflective objects, the laser is selected as the measuring light source. The relative coordinate information of the gear measuring point is obtained using laser triangulation method. In order to get the information of all parts of the gear, by the circular motion of flotation turntable and the lift linear motion of precision electric lift table, data scanning of the gear lead can be completed. In order to obtain absolute coordinates of the gear, the measuring calibration algorithm is proposed to calculate the positional relationship between the sensor and the gear pitch circle. The results show that the proposed measuring method can meet the requirements of high-precision and Non-destructive testing in industry and can be able to classify the gears. And the proposed method can be able to apply to high-precision dimensional inspection system of other metallic reflective objects.