The invention discloses a spheroidizing annealing method for cold heading steel containing B. The spheroidizing annealing method comprises the following steps that the cold heading steel containing Bis heated to be more than or equal to 751 DEG C, and the temperature keeping is calculated according to the effective section thickness of 3.3-4.3 mm/min; the cold heading steel containing B is fast cooled to be smaller than or equal to 200 DEG C; then the cold heading steel containing B is heated to 700-746 DEG C, and the temperature is kept for 6-20h; and finally, the cold heading steel containing B is cooled slowly with a furnace. By the adoption of the method, the distribution condition of carbide particles in the steel is changed by controlling the cooling and temperature speed, so that the carbide particles are more evenly distributed in the matrix, and the segregation of carbides at grain boundaries is reduced, so that the plasticity is enhanced; and spheroidizing annealing can be well realized without plastic deformation.