Laser cladding of Co-base alloy on the sealing surfaces of nuclear valve clacks has been performed with a 5KW CO2 transverse flowing laser. The laser cladding was compared with plasma spraying. Both laser cladded and plasma sprayed zones were characterized by optical and scanning electron microscopes. The high temperature impact-slide wear resistance of laser cladded and plasma sprayed coatings were studied. The experimental results showed that compared with that of plasma sprayed coating, the laser cladded coating has higher microhardness, more uniform microstructure, smaller grain size, lower dilution rate, and fewer pores and impurities. The experimental results also showed that the weight loss of plasma sprayed coating during the high temperature impact-slide wear is two times larger than that of laser cladded coating.