The invention provides a method for calculating critical flowback velocity of fracturing fluid. The method includes the following steps: step 1, performing a settling velocity experiment of a proppingagent to determine the settling velocity of the propping agent; step 2, simplifying a settling model of the propping agent in a crack; step 3, simplifying a settling model of the propping agent in ahole; and step 4, deducing a critical flowback velocity calculation formula. The method eliminates the impact of uncertainties in current field experience on flowback velocity, determines the criticalvalue of the flowback velocity, and solves problems of sand spouting in stratums caused by the over quick flowback velocity.