Based on the tunable diode laser absorption spectroscopy technology, a cloud water content detection system is developed in this paper. A 1 368.6 nm distributed feedback semiconductor laser was employed as detection light source, an orthogonal lock-in amplifier based on TLC7528 chip is designed, which improves the stability of measurement and the ability of restraining noise;The single board realizes the functions of laser driving, harmonic signal processing and concentration inversion. The system carries out on-line detection at different concentrations and temperatures, the experimental results show that the response time of the system is about 10 s, the error of water content is less than 5% in the range of 0~16 g/m3, and it can work normally under the condition of －55~+60℃. The device has the advantages of small size, high detection accuracy, fast response speed, and performance unaffected by temperature, which meets the needs of airborne cloud detection.