Well-crystallized FeS2 powders are synthesized via solid state reaction. Influence of particle size on electrochemical performances has been conducted. Compared with other anode materials, FeS2 powder with mean particle size of 0.28μm exhibits high coulombic efficiency, initial discharge specific capacity, low polarization and enhanced electrode process kinetics. The enhanced electrochemical properties are attributed to the dense powder packing, better electrical contact and relative stable structure during cycling process. Smaller FeS2 particles (0.078 and 0.071μm) have difficulty in dispersing and mixing with carbon black and binder and less dense packing state, leading to a decrease of reactive contact surface area and poor electrochemical performance.