This utility model discloses an adjustable plastic bracket, including a main body, a lifting mechanism, and a placement mechanism. The lifting mechanism includes a lifting frame, a rotating rod, a first spring, a locking block, a driven block, and a positioning component. The positioning component includes a driving block, a second spring, and a connecting plate. The placement mechanism includes a placement frame, a locking block, a pushing screw, and a placement platform. Under the mutual adjustment of the above mechanisms, the height adjustment function of this device allows the bracket to be customized according to the user's needs. In addition, once the device is adjusted to a suitable height and locked, the bracket can remain stable, avoiding height changes due to accidental collisions or movement, and ensuring the stable placement of equipment and items.