The invention relates to a method for controlling the surface temperature of a casting blank at a straightening point of a continuous casting machine, and belongs to the technical field of continuous casting billet quality control. The method is particularly suitable for continuous casting of crack sensitive steel when a long air-cooling area is formed in front of the straightening point of the continuous casting machine. In order to solve the problem that the traditional secondary cooling parameter water distributing method cannot sufficiently control the cooling process of the crack sensitive steel, the invention provides an improved secondary cooling parameter water distributing method. The method can ensure that the surface temperature of each cooling sections of the casting blank reaches the set target temperature in the cooling process at a casting speed and the surface temperature of the casting blank at the straightening point avoids a brittleness temperature range of the cast steel, and also can ensure that when the actual casting speed is deviated from the casting speed, the surface temperature of each cooling section of the casting blank is close to the set target temperature, the cooling rate of the casting blank in each cooling section is basically unchanged and the surface temperature of the casting blank at the straightening point stably avoids the brittleness temperature range of the cast steel. By the method, the probability of crack defects of the casting blank when the casting speed is unstable is reduced, so that the quality of the casting blank is improved.