Aiming at the heterogeneous traffic flow composed of connected and autonomous vehicles (CAVs) and human-driving vehicles (HVs), by analyzing the characteristics of different methods for the stability of heterogeneous traffic flow, the urban heterogeneous traffic model is constructed by the digital twin technology, and the safety and stability of complex heterogeneous traffic flow are explored and solved with the help of simulation testing tools. Based on the construction of the heterogeneous traffic flow model framework by the digital twin technology, combined with the operation mechanism of the digital twin, the paper reveals the operation mechanism of the internal physical entity and virtual space of the digital twin. Using the digital twin technology, an abundant test and verification environment is built, and the driverless development software PanoSim is used to test the heterogeneous traffic flow model. The test results show that the digital twin technology can effectively solve the safety problem of heterogeneous traffic flow by constructing virtual complex driving scene under the condition of limited resources.