A linear motion system, comprising: a guiding member; a moving member slidably disposed on the guiding member, wherein the moving member and the guiding member together form at least one circulation path, and when the guiding member moves with relative to the moving member, the moving member generates a linear movement with relative to the guiding member; a plurality of rolling members (13a, 13b) accommodated in the at least one circulation path; a controller; at least one preload sensing member disposed on the moving member, wherein the at least one preload sensing member detects a preload value generated by the rolling members (13a, 13b) and applied to the moving member, and outputs a detecting signal to the controller; and a preload adjusting module comprising a preload driver and an adjusting assembly, wherein the preload driver and the adjusting assembly are disposed on the moving member individually; wherein the controller controls the preload driver to adjust the adjusting assembly according to the detecting signal, so as to adjust the preload value to a preset value, characterized in that the moving member comprises two nuts (12a, 12b) and a carrier body, the carrier body has a through hole, and the nuts (12a, 12b) are individually disposed in the through hole; the at least one preload sensing member is disposed on at least one of the two nuts (12a, 12b) and electrically connected with the controller; wherein the preload driver is disposed on the carrier body and electrically connected with the controller; the adjusting assembly comprises an adjusting member disposed on one of the two nuts (12a, 12b) and tightly fitted to a periphery of the nut. a guiding member; a moving member slidably disposed on the guiding member, wherein the moving member and the guiding member together form at least one circulation path, and when the guiding member moves with relative to the moving member, the moving member generates a linear movement with relative to the guiding member; a plurality of rolling members (13a, 13b) accommodated in the at least one circulation path; a controller; at least one preload sensing member disposed on the moving member, wherein the at least one preload sensing member detects a preload value generated by the rolling members (13a, 13b) and applied to the moving member, and outputs a detecting signal to the controller; and a preload adjusting module comprising a preload driver and an adjusting assembly, wherein the preload driver and the adjusting assembly are disposed on the moving member individually; wherein the controller controls the preload driver to adjust the adjusting assembly according to the detecting signal, so as to adjust the preload value to a preset value, characterized in that the moving member comprises two nuts (12a, 12b) and a carrier body, the carrier body has a through hole, and the nuts (12a, 12b) are individually disposed in the through hole; the at least one preload sensing member is disposed on at least one of the two nuts (12a, 12b) and electrically connected with the controller; wherein the preload driver is disposed on the carrier body and electrically connected with the controller; the adjusting assembly comprises an adjusting member disposed on one of the two nuts (12a, 12b) and tightly fitted to a periphery of the nut.