The invention discloses a Ti(C,N)/Cr(C,N) composite gradient wear-resisting alloy layer and a preparing method thereof. The alloy layer comprises a Ti-Cr deposition layer, a Ti(C,N)/Cr(C,N) gradient ceramic layer and a C,N reinforcing layer from top to bottom sequentially. The preparing method comprises the steps that firstly, a C,N reinforcing layer is injected to the surface of a powder metallurgy gear in an ion manner; secondly, a Ti-Cr alloy layer is prepared on the surface of the C. N reinforcing layer in a double glow plasma alloying method. C,N atoms easily have an interaction effect with alloy elements, and nitrides and carbide are generated. In the plasma alloying process, Ti and Cr which are sputtered out have a reaction with C,N which can be subjected to ion injection, and the gradient ceramic wear-resisting alloy layer with the Ti(C,N)/Cr(C,N) composite structure is formed. The wear resisting property of the powder metallurgy gear can be greatly improved, and the service life of the gear is greatly prolonged.