On the basis of analyzing the mechanical structure of the existing 3D printer, a unipolar coordinate 3D printer was designed and the prototype was made. Mechanical structure design was done using SolidWorks platform. After numerous debugging and printing experiments, the factors influencing the printing precision and the effect on model quality were summarized. The mechanical structure of the 3D printer combines the advantages of the existing rectangular coordinate and polar coordinate structure, which is composed of a single rotation axis and a linear motion axis, making the structure more stable. In the software algorithm matching the mechanical structure, the transformation of polar coordinates and cartesian coordinates only needs to be carried out once, control procedures are simpler.