The performance evaluation system of SpaceWire bus based on dual-route unit was studied. The definition of dual-route unit was given and the computation method of data transmission time and resource consumption of the route system based on dual-route unit was derived during the study. The performance evaluation system of multi-route topological system based on dual-route unit was derived; the simulation platform of dual-route unit system was built by using the Monte-Carlo method, and the performances of route unit with different interface configurations were simulated. Study results show that the performance of SpaceWire bus can be evaluated through using the transmission time and resource consumption indexes based on dual-route units, and also that an aimed configuration exists such that the system performance can be optimized to the best when different interface configurations are considered.