The invention relates to a sliding rail for automobile seats and belongs to the technical field of automobile seat accessories. An upper guide rail is composed of a short folded edge, a long folded edge and an upper installation surface, wherein rollways are respectively formed on the short folded edge and the long folded edge, a first lock pin hole is arranged in the middle of the upper installation surface, and an unlocking block fixing lug, a spring fixing hole and an unlocking rod hole are arranged on the long folded edge. A lower guide rail is composed of a long folded wall, a short folded wall and a lower installation surface, wherein ball grooves are respectively formed on the long folded wall and the short folded wall, and a locking groove is arranged in the middle of the lower installation surface. A locking device comprises a lock pin, a compressed spring, a limit plate, a return spring, an unlocking block, a wrench, an unlocking rod and a connection sleeve. A ball frame is formed by balls, an upper ball positioning roll and a lower ball positioning roll which are all arranged in a containing cavity defined by the rollways and the ball grooves. The sliding rail for automobile seats has the advantages of being high in strength, small in gap, good in synchronism, free of self locking, small in step pitch, few in parts, convenient to assemble and process, low in cost and wide in application range, and an upper sliding lateral surface can also serve as an installation surface.