A wear-resistant and corrosion-resistant Mo2NiB2-Cr7C3 composite coatings were prepared on the substrate of 45# steel by laser cladding. The effects of laser cladding parameters including scanning rates of 3 and 4 mm/s and the addition of Cr7C3 particles on the microstructure and properties of the cladding coatings were investigated. The SEM, EDS, XRD, micro-hardness tester, friction and wear tester and electrochemical workstation were used to character the microstructure, composition and properties of the cladding coatings. Results showed that a fusion transition zone was appeared between the cladding coating and the substrate, consequently leading to a good metallurgical bond. The main phases in cladding coating were Mo2NiB2, Cr7C3 and {FeNi} phases. The Mo2NiB2 and Cr7C3 phases preferred gathering in the middle of the cladding coatings. And the laser scan rate of 3 mm/s brought in the increased content of {FeNi} phase in the coating. From top layer to bottom layer of the coating, the micro-hardness firstly increased and then decreased, in which the highest micro-hardness could reach more than 1300HV0.1, 6 times higher than that of 45# steel (220HV0.1). Compared with 45# steel, the cladding coatings possessed the lower friction coefficient and wear loss and better corrosion resistance. Especially, the Mo2NiB2-Cr7C3 coating prepared at 4 mm/s possessed the highest micro-hardness, the best wear resistance (friction coefficient of 0.66, scratch depth of 8.6 μm) and the best corrosion resistance (Jcorr is one order of magnitude lower than 45# steel). Therefore, the high laser scanning rate (4 mm/s) and the addition of Cr7C3 particles could effectively enhance the mechanical properties and corrosion resistance of the Mo2NiB2-Cr7C3 coatings, consequently fulfilled the surface modification of 45# steel.