Abstract: Under simulated space conditions such as atom oxygen and high vacuum, the tribological properties of the composite materials of micro-MoS₂, MoS₂ nano-ball and MoS₂-IC are studied in this paper. The results show that the composite material of MoS₂ nano-ball has the best anti-wear properties. The MoS₂-IC has also a good wear resistance, while micro-MoS₂ is the worst regarding the wear resistance. However, they are not very much different with respect to the friction reducing performance, with MoS₂ nano-ball showing only a slightly lower friction coefficient. MoS₂-IC is transferred to the counter rubbing surface and forms a transferring film during the rubbing process, leading to a better anti-wear performance than the micro-MoS₂ composite materials. The excellent tribological properties of the MoS₂ nano-ball result from its particularly good spherical structure.