For the flexible requirement to the photoelectric instrument, the vehicle platform is needed to load the transmitting light path and receiving light path, often including several lasers and many mirrors. There have been some methods to measure the parallelism of optical paths for the fixed platform which is not suitable for the vehicle platform. Therefore, a certain improvement should be made to the measurement methods for parallelism of optical paths for the vehicle-based photoelectric system. In our system, the optical paths of four laser systems and three imaging system need to be adjusted into the same line or paralleling each other. Therefore, the requirements for the vehicle platform are more complicated for the parallel test. According to the feature of the platform based on the vehicle, a systemic method was presented for the parallel test. The measurement results show that these methods are simple and practical for the measurement of parallelism in vehicle-based photoelectric devices and the measurement errors between each light path are all less than 15 μrad.