The invention discloses a double-diaphragm spring brake air chamber for a commercial vehicle brake system. The double-diaphragm spring brake air chamber comprises a connecting cover (1), a front push plate, a central shaft (2) and diaphragms (5), the central shaft (2) penetrates a central hole of the connecting cover (1), the front end of the central shaft is connected with the front push plate through a screw, a rear push plate A (4) and a rear push plate B (6) are fixedly clamped at the rear end of the central shaft (2) through screws (3), and the diaphragms (5) are clamped between the rear push plate A (4) and the rear push plate B (6). By the aid of the technical scheme, product structures are simplified, product failures are decreased, production cycle is shortened, productivity and durability of products are improved, so that product performances are improved, the service lives of the products are prolonged, and a truck brake system is safer.