Abstract: The wear characteristics of laser transformation hardened, quench-tempered and untreated 45# carbon steel have been studied under 98N of load, 100 times per minute of reciprocating frequency (reciprocating distance is 0.1 metre) and 6000 times of reciprocating, the results are as follows: a. The martensite was formed on the surface of 45# carbon steel after laser transformation hardening treatment, therefore the microhardness of the surface increases by 2-3 times. b. The laser transformation hardening treatment results in the change of wear course of 45# carbon steel. Under dry friction,the wear resistance of the treated 45# carbon steel is higher than that of untreated steel by one order of magnitude. c. The wear rate of quench-tempered sample increases rapidly with increasing load. When the load is less than 294N, the wear rate of laser transformation hardening treated sample increases slowly, above 294N of load the wear rate increases significantly. d. Under given testing conditions and the reciprocating frequency is less than 500 times per minute, the wear rate of transformation hardening treated sample is always less than that of quench-tempered sample. When the reciprocating frequency is more than 600 times per minute, both of wear rates make no much difference.