The invention discloses a method and a system for recovering high-temperature sensible heat of molten blast furnace slag. The system comprises a blast furnace slag runner, a slag hopper, a slag hopper lifting mechanism, a quenching unit, a slow cooling unit, a cold slag particle circulation unit, a cyclone dust collector, a waste heat boiler, a condensing unit, a circulating fan, and a booster fan. The method for recovering waste heat comprises the following steps of: crushing and quickly cooling the molten blast furnace slag in the quenching unit in a composite way of a rotary crushing wheel, high-pressure cold air, a slag trap, cold slag particles and cooling water, and fully exchanging heat with solidified blast furnace slag in the slow cooling unit by using cooling air; and allowing high-temperature air which comes out of the quenching unit and the slow cooling unit to enter the waste heat boiler and performing heat exchange, transforming into steam or electric power and then outputting. The subsequent utilization of blast furnace slag and the waste heat recovery efficiency are synchronously considered, condensed water is recycled, finished slag does not contain water or only contains a small amount of water, the granulation effect of the slag is better, and the contradiction between intermittent slagging and continuous heat production of blast-furnace ironmaking is resolved.