Abstract: An opening and closing control mechanism for the project window which mainly comprises a slide frame, a slide block, a retaining block, a pivoted force arm, a carrier arm, a support arm and a connecting arm in an effort to improve the carrier arm which works as a fixed pivot at the near end of sash to be able to bear the pushing load. The retaining block, combined with the slide frame, enhances the structural stability of the sash as well as the smoothness of opening and closing movement.