The invention provides a production method of heavy rail steel for a guard rail. The production method comprises the steps that slag materials are added during LF refining operation for preparing high-alkalinity white slag with the binary alkalinity being 3.0-5.0 for refining; when the sulfur content of molten steel is lower than or equal to 0.012 wt%, a slag modifier is added for slag modifying treatment, and the alkalinity of slag is controlled to 1.5-2.0; ferrotitanium is added to control the titanium content of the molten steel to 0.015-0.025 wt%; then soft blowing, discharging out of a station and steel feeding are conducted; and in the step of slow cooling of a cast blank, the cast blank is taken down from a line through a clamp and placed into a slow cooling pit for slow cooling treatment, the temperature for placing the cast blank into the pit is not lower than 700 DEG C, the temperature for discharging the cast blank out of the pit is not higher than 150 DEG C, and thus good thermodynamic conditions for diffusion of hydrogen in the cast blank are provided. According to the production method, the RH or VD refining step in the prior art is omitted, the production technological process of the heavy rail steel for the guard rail is simplified, and the production cost is reduced; and various impurities in the cast blank are controlled to 2.0 grade or below, center segregation and porosity defects in the cast blank are effectively reduced, and the requirement for the quality of the guard rail is completely met.