The microstructure and tribological properties of space copper-based friction material fabricated by Powder Metallurgy technology were studied using optical metallographic microscope and MM-1000-type tribo-tester, respectively. The results are shown as follows: The lubricant MoS2 was resolved during sintering, resulting in the loss of S element. MoS2 and its resolvents reacted with other components into some new compounds which contribute to the tribological properties of friction material. The lubrication mechanism of these new compounds showed essential difference in comparison to that for MoS2; the friction coefficient was higher under atmospheric condition than that under vacuum conditions, but almost the same under low and high vacuum conditions. It decreased under both atmospheric and low vacuum conditions with the increase of load. The environmental temperature had insignificant effect on the friction coefficient; under atmospheric condition as load increased, the mass loss of material decreased linearly, then increased. With regard to low vacuum condition as load increased, the mass loss of material increased, then decreased; the stable coefficient of friction material under vacuum condition was higher than that under atmospheric condition.