A printer mechanism having multiple hosts on a common conveying platform, the printer mechanism comprising: the conveying platform used for conveying a printing substrate with a conveyor belt driven by a power mechanism, and an inkjet system composed of a number of modular connectable hosts connected to each other, each host comprising at least a main cabinet beside the conveyor belt and an upper cabinet extending from a side of the main cabinet, and the upper cabinets of the whole inkjet system being distributed in parallel to each other above the conveying platform, the hosts having generally a C-shape or an inverted U-shape so that the hosts can be quickly pulled out of or pushed into the conveyor belt for addition or replacement of the hosts, an inkjet printhead carriage system composed of a number of modular connectable inkjet printhead carriages, installed and connected to each other, each inkjet printhead carriages having a ink nozzle module, the inkjet printhead carriage system being disposed at the inkjet system and above the conveying platform, and each inkjet printhead carriage being correspondingly connected to each host one by one in a modular manner, characterized in that the inkjet printhead carriage system comprises a support base and a number of inkjet printhead carriages, each of the inkjet printhead carriages is provided with a lifting frame, a number of installation sites arranged in parallel to each other are disposed at a side face of the support base, the lifting frames are correspondingly installed to the installation sites one by one, each of the installation sites is provided with a screw rod, the screw rod supports the lifting frame, and a transmission mechanism for transmission of a synchronous action is disposed between the screw rods to simultaneously adjust each inkjet printhead carriages in a height direction. the conveying platform used for conveying a printing substrate with a conveyor belt driven by a power mechanism, and an inkjet system composed of a number of modular connectable hosts connected to each other, each host comprising at least a main cabinet beside the conveyor belt and an upper cabinet extending from a side of the main cabinet, and the upper cabinets of the whole inkjet system being distributed in parallel to each other above the conveying platform, the hosts having generally a C-shape or an inverted U-shape so that the hosts can be quickly pulled out of or pushed into the conveyor belt for addition or replacement of the hosts, an inkjet printhead carriage system composed of a number of modular connectable inkjet printhead carriages, installed and connected to each other, each inkjet printhead carriages having a ink nozzle module, the inkjet printhead carriage system being disposed at the inkjet system and above the conveying platform, and each inkjet printhead carriage being correspondingly connected to each host one by one in a modular manner, characterized in that the inkjet printhead carriage system comprises a support base and a number of inkjet printhead carriages, each of the inkjet printhead carriages is provided with a lifting frame, a number of installation sites arranged in parallel to each other are disposed at a side face of the support base, the lifting frames are correspondingly installed to the installation sites one by one, each of the installation sites is provided with a screw rod, the screw rod supports the lifting frame, and a transmission mechanism for transmission of a synchronous action is disposed between the screw rods to simultaneously adjust each inkjet printhead carriages in a height direction.