The invention provides a crystallizer cooling water control device and method. The crystallizer cooling water control device comprises a crystallizer for continuous casting, a water inlet main circuit is connected to the inlet end of the crystallizer for continuous casting, and the inner arc, the outer arc, the left side and the right side of the crystallizer for continuous casting are connected with an inner arc water return branch circuit, an outer arc water return branch circuit, a left side water return branch circuit and a right side water return branch circuit respectively. A first temperature sensor used for detecting the temperature of inlet water is arranged on the main water inlet circuit, and second temperature sensors used for detecting the temperature of return water of all branch circuits, electromagnetic flow meters used for calculating the flow of the return water of all the branch circuits and pneumatic film adjusting valves are arranged on the inner arc water return branch circuit, the outer arc water return branch circuit, the left side water return branch circuit and the right side water return branch circuit respectively. The cooling water amount of the inner arc, the cooling water amount of the right arc, the cooling water amount of the left side and the cooling water amount of the right side of the crystallizer are calculated according to the factors such as the steel type, the pull speed, the inlet water temperature, the inlet water and return water temperature difference, the molten steel superheat degree and the size of the cross section of a blank and PID adjustment of the water amount is realized through the electromagnetic flow meters and the pneumatic adjusting valves. During casting, casting blank heat transmission is improved and the occurrence rate of surface defects is reduced.