In order to obtain the real optical characteristics of digital micro-mirror devices (DMD), a test method for the reflection characteristics was proposed, and an experimental device was built to test the relative reflection efficiency of digital micro-mirror devices. Firstly, the test optical path was built. Then, the optical path was used to measure the spot energy distribution curves received by the camera when the digital micro-mirror device and the aluminum mirror were used as the reflecting elements respectively, and the curves were integrated. Finally, the relative reflection efficiency of the digital micro-mirror device was obtained by dividing the integral values obtained under the two test conditions. The test results show that the relative reflection efficiency of the digital micro-mirror device is 45.33% when using a 632.8 nm wavelength laser as the light source and 71.75% when using the white LED as the light source. After many tests, it is found that the repeatability precision of the two test modes is about ± 5%. The above test results can be used as a reference for the calculation of energy transfer efficiency and device selection when using digital micro-mirror devices to develop related instruments in the future.