The invention relates to a pair of trousers capable of protecting waist. An inflatable bag body is spliced to the rear waist portion of the trousers; a connecting edge of one side of the inflatable bag body is spliced with the waist of the trousers and the other side is turnable; a lining is spaced between the inflatable bag body and a human body when the inflatable bag body is turned downwards and is canceled in the trousers; an air nozzle is arranged on the inflatable bag body; and the inflatable bag body, after being turned upwards and inflated, has a cambered surface in correspondence to the waist of the human body. Two or more connecting loops are arranged between the upper and lower layers of the inflatable bag body for connecting the upper and lower layers. The trousers disclosed by the invention have the advantages that by virtue of a canceled semi-movable inflatable bag body which is arranged on the inner side of the lower part of the rear waist of the trousers, a three-dimensional bag body is formed after inflation, so that waist of a person sitting on a seat is supported. The pair of the trousers is designed in accordance with the demand of ergonomics; and the pair of trousers is convenient for carrying and is capable of relieving fatigue in the waist anytime and anywhere.