By measuring hardness of high Cr-W wear resistance cast iron after treated with different sub-critical treatment process, sub-critical treatment process of high Cr-W wear resistance cast iron was discussed. The results show that the secondary hardening of the cast iron appears under the proper sub-critical treatment process. As a result, the high Cr-W wear resistance cast iron can obtain higher hardness under sub-critical treating at 570 ℃ for 5 h. By measuring hardness of high Cr-W wear resistance cast iron after treated with different sub-critical treatment process, sub-critical treatment process of high Cr-W wear resistance cast iron was discussed. The results show that the secondary hardening of the cast iron appears under the proper sub-critical treatment process. As a result, the high Cr-W wear resistance cast iron can obtain higher hardness under sub-critical treatment at 570 ° C for 5 h.