The invention provides a print head protecting device for a full-automatic digital blueprint printer. The protecting device is of a triangular block structure, a printing face, a protecting face and a cleaning face are formed on the three faces of the triangular block structure, and a through hole is formed in the center of the longitudinal section of the triangular block structure in the axial direction and used for installing a rotation shaft, so that the printing face, the protecting face and the cleaning face rotate around the rotation shaft for switching. According to the print head protecting device, a print head can be effectively protected through the print head protecting device shaped like a triangular block and a downwards inclined paper channel.