Abstract: To achieve the target of replacing bronze to steel in worm transmission,superfine manganese phosphate conversion coating and ferrous sulfide coating were prepared on the surface of 20Cr steel.The tribological properties of the coatings were compared using a friction and wear tester.SEM and EDX were adopted to analyze the morphology and compositions of the original and worn surfaces of the coatings.The phase structure of the coating was studies by XRD.The results show that two coatings had good antifriction and antiwear performance under the load less than 300 N.When the load was larger than 500 N,superfine manganese phosphate coating had good ability of antifriction and antiwear,and performance of the ferrous sulfide coating was low.