A level adjustment system. The level adjustment system includes an adjustable pin chuck, an evacuation device, a level detection device and a length control device. The adjustable pin chuck includes a base and a variable pin to support a substrate. The base includes a recess and an evacuation channel connected thereto. The variable pin is disposed in the recess. The evacuation device is connected to the evacuation channel to evacuate the recess, such that the substrate is attached to the base and variable pin. The level detection device is disposed on the adjustable pin chuck to detect the horizontality of a target surface of the substrate. The length control device is electrically connected to the level detection device and variable pin. The length control device changes the length of the variable pin to adjust level of the target surface of the substrate according to the detected horizontality.