The invention provides a dynamic waterproof performance detection method for a fire extinguishing protection boot. The method comprises the following steps of: 1, marking a mark line segment, wherein a mark pen is used for marking a line segment on the outer side surface of the bottom of a sample boot, and two ends of the line segment are respectively the center of a boot head and the center of a boot heel; 2, determining a mark point from the line segment marked in the step one, wherein the distance from mark point to the end point, at the center of the boot heel, of the line segment marked in the step one is the average distance from the center of the heel of the fire extinguishing protection boot to the center of a boot sole; 3, obtaining a bending position line, wherein the mark point is moved along the line segment in the step one to the direction of the boot heel for 5 mm, a vertical point is obtained, and the line perpendicular to the line segment in the step one through the vertical point is the bending position line; and 4, carrying out bending test from the bending position line determined in the step 3. The dynamic waterproof performance detection method for the fire extinguishing protection boot has the advantages that the detection method is standard, and the consistency of detection results is good.