Due to the inability to conduct sufficient road tests (road tests require extremely expensive time and cost), it is necessary to rely on computer simulation systems to assist in the development and testing of autonomous driving systems in a virtual environment. This chapter introduces some modules for building a simulation system. Section 10.1 introduces the simulation of sensors, such as the imaging technology of cameras, the data simulation synthesis of lidar and millimeter-wave radar, etc.; Sect. 10.2 introduces traffic simulation models based on the open-source software SUMO; Sect. 10.3 introduces vehicle and pedestrian CAD models, and discusses the vehicle dynamics of deep learning modeling, and also introduces some research on rendering human bodies and human motion in the field of computer vision; Sect. 10.4 introduces the visualization technology of autonomous driving with the open-source visualization platform of the American online taxi company Uber as an example; Sect. 10.5 introduces the establishment of a road network simulation environment; Sect. 10.6 analyzes the autonomous driving test technology of the scenario library (including the scenario description language OpenSCENARIO and the scenario library example PEGASUS); finally, Sect. 10.7 discusses the neural network method of constructing safety-critical data for digital twins.