To realize the real-time measurement of optical concealment depth for a vehicle under water, an optical concealment depth measurement system for the underwater vehicle was developed. According to the target background contrast transfer theory, the transport properties of the target background contrast in sea water, air and sea were analyzed and a model of underwater optical concealment depth for the vehicle was established. On the basis of the model, required parameters for measuring optical concealment depth of underwater vehicle were analyzed and the measuring methods for the water upward irradiance, water downward irradiance, water body attenuation coefficients, water diffuse attenuation coefficients and underwater vehicle surface reflectivity were designed. Then, an experiment on sea was completed, and it shows that underwater optical concealment depth of the vehicle with a characteristic scale of 12 m ranges from 25 m to 35 m under good weather conditions. The experimental results indicate that the measurement system successfully measures the depth of optical concealment of the vehicle and also is suitable for other submarines. As it avoids the traditional depth measurement mode, the system has stable and reliable operation, improves the conceal ability and measuring accuracy, and provides the supports for underwater flight decision.崔国恒,于德新.非声探潜技术现状及其对抗措施［J］.火力与指挥控制,2007,32(12): 10-13.CUI G H,YU D X.Non acoustic detection technology of submarine and its countermeasures［J］.Fire and Command Control,2007,32(12): 10-13. (in Chinese)