An object of the present invention is to provide an ink jet print system in which quality troubles (e.g. banding and ink overflow) caused by an unsuitable combination of ink and an ink jet recording medium in an ink jet recording apparatus in the case where the ink jet recording medium is an imitation, are obviated on the basis of printing control information obtained from the ink jet recording medium with an information-detecting sensor, and it is possible to prevent the employment of an ink jet recording medium which a user cannot judge to be a genuine product or an imitation. According to the present invention, an ink jet print system can be obtained in which printing information obtained from an image processor and the printing control information of the ink jet recording medium obtained from the information-detecting sensor are processed and on the basis of information of these kinds, the best image is always formed with the ink jet recording apparatus by the use of a genuine product. The printing control information of the ink jet recording medium is preferably a logo print or a cord image print. The ink jet recording medium is preferably of a rolled paper type. The system is stopped when an imitation is used which does not match with the printing control information.