The invention relates to a 42CrMoVNb steel, which can resist a low temperature impact and is used for the variable pitch wind turbine and the yaw bearing ring. The weight percentage for the components of the steel is as follows: C 0.42 to 0.45 percent, Si 0.15 to 0.30 percent, Mn 0.60 to 0.90 percent, Cr 0.90 to 1.20 percent, Mo 0.15 to 0.30 percent, Ni 0.35 to 0.60 percent, V 0.08 to 0.15 percent, Nb 0.03 to 0.06 percent, Cu less than or equal to 0.20 percent, Al less than or equal to 0.05 percent, S less than or equal to 0.015 percent, P less than or equal to 0.015 percent, As less than or equal to 0.015 percent, Sn less than or equal to 0.012 percent, : less than or equal to 20PPM, <H>: less than or equal to 2.0PPM and the rest are Fe and natural impurities. The impact resistant capability of the steel at a low temperature is improved by adding vanadium and niobium to the prior 42CrMoVNb steel. The upper limit value for the carbon content is adopted to help to reach the requirement of HRC 55 to 60 after the surface is quenched and backfired. During the steel smelting, Al, As and Sn are used for slag forming and degassing to increase the content. The Akv detected at minus 40 DEG C by three samples reaches 91J, 97J and 98J respectively, which is exceeds the required value of minus 45 DEG C and is 3.37 times of the standard value. After being commuted, the requirement that Akv is equal to 27J at minus 70 DEG C can also be satisfied. The invention sets a precedent for the development of a steel demanding for an Akv at a lower temperature and fills the domestic gap. The invention is applicable to bearing and mechanical components, in particular to variable pitch wind turbines and yaw bearings.