The invention relates to a wide and thick plate continuous casting machine dry capping method, and belongs to the technical field of continuous casting technologies. The wide and thick plate continuous casting machine dry capping method particularly comprises the following steps and parameters that in the speed reduction stage, according to the actual measurement tundish tons, in cooperation the tundish measurement actual liquid level, the pull speed is reduced to 0.25 m/min; in the low-speed and constant-speed running stage, according to the tundish tons and the actual measurement liquid level, when the depth of the liquid face of molten steel in a tundish ranges from 100 mm to 300 mm, a plug bar is closed, meanwhile, the pull speed is reduced to 0.15 m/min to 0.2 m/min, and low-speed running is kept; and in the speed increasing process, the blank tail is pulled out of a crystallizer, and the pull speed is increased to a target pull speed. The wide and thick plate continuous casting machine dry capping method has the beneficial effects that slag is not wasted, slag fishing is avoided, low-speed weak-cold control is achieved, and therefore the effective improvement of the tail blank quality is achieved, the tail blank flaw detection yield is improved, the tail blank waste cutting amount is reduced, and the metal yield is improved.