A communication and simulation method with an intermediate conversion board as a bridge is proposed to meet the real-time performance and accuracy of the combination weigher simulation in Digital Twin. At first, the control signal of the machinery was sent out by the control board and captured by the intermediate conversion board and then the signal in it was converted and sent to the upper computer . Finally, the model of combination weigher built on the Unity3D in the host computer recognized the data from the conversion board, and thus performed motion simulation of the real machine. To obtain the control signal accurately, the signal was captured by the interrupt on the conversion board, and converted as a fixed format to the upper computer through the Ethernet. To simulate the movement of the combination weigher, the Physics component in Unity3D is used to ensure accurate movement. Finally, the transmission speed in the simulation process of the combination weigher was compared and analyzed. In addition, this method can also be used to simulate high-frequency pulse-driven robots, modular machine tools and other machinery.