Disclosed is a composite steel fireproof door. A door leaf is divided into a left door leaf and a right door leaf. A sealing strip is arranged between the left door leaf and the right door leaf. The sealing strip is arranged along the inner side edge of the left door leaf and attached to the right door leaf when the left door leaf and the right door leaf are closed. The door leaves are provided with frames. The frames are provided with fixing holes. The sealing strip is arranged on the fireproof door so that fire can be prevented and controlled from quickly entering the door, using of the fireproof door is made to be better, and the situation that dense smoke quickly enters the door in case of a fire is avoided. The frames are further arranged on the door leaves so that the door leaves canbe fixed more firmly.