With the development of the domestic and foreign automobile scale, automobile glass type and quantity increased strongly. Optic characteristic of automobile glass is one of the important technical requirements of automobile glass, as a result, the detection of optic characteristics of automobile glass is very necessary. An on-line automatic detection system for automobile glass transmission and reflectivity was proposed. This system was mainly based on the different reflection, absorption and transmission principle when light propagates in different medium, and combined with modern photoelectric detection and digital signal process technology, achieved on-line automatic detection for automobile glass transmission and reflectivity. By simulation verification, this system can detect transmission and reflectivity for automobile glass on-line, moreover, it has high reliability, high precision, high cost performance and easy expansion