The work aims to improve quality of continuous casting billet, extend service life-span of crystallizer and save copper resource. Ni/Al2O3 nano composite coating was prepared on the surface of copper crystallizer by adopting nano composite electroplating technology, and surface morphology of the composite coating was observed with SEM. The effects of nano Al2O3 addition, cathodic current density and electroplating bath temperature on microhardness of the composite coating were studied in single factor method. The friction and wear tests were carried out on pure Ni coating and nano composite coating. A nano composite coating of high hardness and wear resistance was prepared on the surface of copper crystallizer. Microhardness of the composite coating first increased and then decreased as the addition of nano particles increased. When 40 g/L of nano Al2O3 particles was added, microhardness of the composite coating reached the maximum value of 384HV. As nano particles were present in the electroplating bath, the microhardness changed little with the change of current density and electroplating bath temperature. Provided with the same friction and wear conditions, the friction coefficient of nano composite coating and pure Ni coating was about 0.41 and 0.7, respectively; wear loss of nano composite coating was about 1/2 of that of pure Ni coating. The addition of nano Al2O3 material in Ni-based coating can significantly improve hardness and wear resistance of composite coating.