The invention discloses a blade protective cover angle correcting device of a mower blade protective cover automatic loader. The blade protective cover angle correcting device of the mower blade protective cover automatic loader comprises a third guide rail mounting plate and a fourth guide rail mounting plate fixed on a frame in parallel; the third guide rail mounting plate and the fourth guide rail mounting plate are each provided with one fourth X-direction linear guide rail fixedly; fourth mounting plates are fixed to slide blocks of the fourth X-direction linear guide rails; the fourth guide rail mounting plate is fixedly provided with first X-direction cylinder mounting bases on the outer sides of the fourth X-direction linear guide rails; and first X-direction cylinders are fixed to the first X-direction cylinder mounting bases. Through the above manner, the blade protective cover angle correcting device of the mower blade protective cover automatic loader can replace workers to correct angles of blade protective covers, greatly improves the productivity, increases the product yield, and saves labors.