Abstract: Mechanisms of the influence of transmission medium, system infection, interchannel skew and single event transient on bit error rate (BER) in SpaceWire system are analyzed. Because there is no high confidence level and uniform BER test method in spaceflight system, an effective test method is proposed by introducing the statistical confidence principle credits. This method can realize the high confidence level and efficiency of the bit error rate test, which is important to the application of SpaceWire devices in spaceflight system.