Abstract: A thin film deposition system and a method for deposit a thin film are disclosed. A thin film deposition system includes a source material feeder configured to feed source material, a source gas feeder comprising a vaporizer connected with the source material feeder to evaporate the source material fed by the source material feeder, a thin film deposition device connected with the source gas feeder to deposit the evaporated source material fed by the source gas feeder on a treatment object, vaporizer exhaustion unit having an end connected with the vaporizer to ventilate an inside of the vaporizer, and a pressure adjuster connected with the exhaustion tube to adjust the pressure of the exhaustion tube to control the velocity of source material fed to the vaporizer.