The life of a satellite electric slip ring is approximately 100,000 rounds. To verify the reliability of a column slip ring at the end of one million rounds, we performed a two-million-round life test. As slip rings contain both a single brush wire and a brush bunch, this test compareed the transmission error of different types of signals that pass through single brush wires and brush bunches. The structure of the brush wire was vital in determining the transmitting stability of a space electric slip ring. This study verified the main influencing factors, such as different temperature, revolving speed, and vacuum performance. The transmission errors of CAN and RS422 signals indicate that brush bunch rings, which are characterized by a 0.6% voltage drop and no transmission error, are more stable than single brush wire rings in a vacuum with a signal transmission speed of 500 kbps. The maximum voltage drop of single brush rings is over 100% and transmission errors are approximately 16.1%. This proves that the design of brush bunches can effectively improve the reliability of signal transmission and prolong the service life of slip rings; this knowledge is of significant value in determining the reliability of satellites.