With the continuous development of the digital twin technology at this stage, research and applications surrounding digital twins have gradually become a hot spot. Because traditional autonomous driving test methods have various defects in terms of functionality, safety, and test cost, this article proposes a construction method of the digital-twin automatic driving test environment based on mixed reality in light of the basic characteristics of digital twins and the test method of autonomous driving. The autonomous driving information in the actual environment is mapped to the virtual scenario through spatial coordinate mapping, collision detection model, and virtual scene registration. In addition, the corresponding mixed reality based automatic driving test model is constructed. The collision test demonstrates that the mixed reality system has interactive features. The performance of the system at sampling frequencies of 50 ms, 200 ms, and 1000 ms is compared and analyzed. Experiments show that the algorithm in this study has better operating frame rate characteristics at the sampling frequency of 200 ms or above.