With the continuous development of additive manufacturing technology, an increasing number of fields integrated with 3D printing, providing new opportunities for its advancement. In this paper, a novel mobile 3D printing robot was proposed that cooperated a planar five-bar mechanism to overcome limitations of traditional 3D printers, such as immobility and restricted working range. The mobile 3D printing robot had a unique working mode that utilizes a planar five-bar mechanism to follow the trajectory of a planar model. The robot controls a linear model to achieve the lifting of the ejector, enabling the completion of the manufacturing process. Furthermore, when paired with a mobile platform, the robot had the ability to extend infinitely on the x and y axes. Trajectory simulations and work demonstrations were conducted on the robot, showcasing its ability to achieve complex trajectories and manufacture large-scale models.