The tribological properties of PEEK composites filled with CaCO3 whisker in various content of 0-30%(weight percent) were investigated.The composite specimens were prepared by compression molding. Tribological testing of composites in water lubrication against carbon steel ring was carried out on a MM200 block-on-ring apparatus.Data on neat PEEK were also included for comparison. The morphologies of wear traces were observed by SEM.It was observed that inclusion of CaCO3 whisker significantly improved the wear resistance and reduced the friction coefficient of PEEK composites under water lubricated condition. With an increase in CaCO3 whisker contents, the specific wear rate of composites decreased and showed minima for 20% CaCO3 content as 5.2% of that for PEEK. In terms of friction applications under water lubrication, the optimal content of CaCO3 whisker in PEEK composites should be recommended as 15% to 20%.The SEM observation of the wear traces indicated that the transfer film is not the main reason for the enhancement of wear resistance of the composites in water lubrication.CaCO3 whisker contributed to increase the load-carrying capacity and abate the scuffing and adhesion of PEEK composites, finally led to a significant improvement of the wear resistance.