A projection system includes a control module, a projection tube, an aiming driver, an observation device and an observation driver. The control module is configured to issue a first control command and a second control command. The aiming driver is electrically connected to the projection tube and configured to control, in response to the first control command, a projection viewing-line of the projection tube to be aligned with a calibration point. The observation driver is electrically connected to the observation device and configured to control, in response to the second control command, an observation viewing-line of the observation device to be aligned with the calibration point. The projection tube and the observation device are controlled asynchronously.