The invention discloses a pattern recognition based overdrawn preventing alarm method for winch rope of road rescue equipment. The method includes steps of 1, marking geometric patterns on the periphery of a wheel on the outer side of a winch rope groove; 2, arranging a pattern collecting device on the outer side of the winch rope groove of the road rescue equipment, wherein the collecting area of the pattern collecting device is greater than the single geometric pattern mark in size and an area greater than the single geometric pattern mark is set as an interest area in the collecting area so as to make the interest area can only include one geometric pattern mark; 3, identifying the types of the geometric pattern marks included by the interest areas in each frame of image collected by the image collecting device; 4, identifying collected images continuously and obtaining a geometric pattern mark change sequence; and obtaining winch shaft rotation direction and rotation angle according to the geometric pattern mark change sequence; 5, calculating the winch shaft rotation direction and rotation angle and giving safety alarm when the loop number of the winch rope is smaller than a threshold value.