Abstract: By combining theoretical analysis with experimental verification, the key influencing factors of efficiency of building 3D printing based on fused deposition modeling (FDM) were analyzed and studied. In the part of theory analysis, on one hand, the formula of the efficiency of 3D printing was proposed; on the other hand, various factors influencing the efficiency of 3D printing were analyzed systematically. In the part of experiments, by setting different operating modes, the effect of different factors on the efficiency of 3D printing under the condition of controlling other factors unchanged was carried out on quantitative experiment respectively. The results indicate that many factors could influence the efficiency of 3D printing, mainly including the preparing time before 3D printing, the size of printing object, the complex degree of printing object, the layer resolution, print strength and print pattern and other factors, and the influence degree of each factor was different. Finally, the research on printing efficiency in the field of building 3D printing was prospected.