The invention relates to a method for reducing Brinell hardness of a CrMo serial hot-rolled rod. A production process of the CrMo serial hot-rolled rod comprises a heating process and a rolling process; the heating process includes a heating section and a soaking section; and the reduction of the Brinell hardness of the CrMo serial hot-rolled rod needs to control the temperature of the heating section within 1050-1120 DEG C, to control the temperature of the soaking section within 1050-1110 DEG C and to control the final rolling temperature of the rolling process within 900-950 DEG C. The method can reduce the Brinell hardness of the CrMo serial hot-rolled rod from about 310 HBW to about 260 HBW; and compared with a controlled rolling and controlled cooling process, the method needs no controlled cooling process transformation for a production line, that is, 3-5 water cooling boxes and control equipment are added on the production line according to the process arrangement, so that the energy consumption can be reduced by 5-10%, the production cost is reduced, and CrMo steel with various specifications can be produced. Attention: the Brinell hardness of the rod is a Brinell hardness value in the 1/2 radius place of the cross section of the rod.