Abstract: To improve the dimensional accuracy and surface quality of fused deposition modeled parts, a cylindrical sample made from polylactic acid was used as an experimental object, and the effects of layer thickness, nozzle temperature, printing speed and filling rate on the dimensional accuracy of parts was studied by means of an orthogonal experimental design method. An optimal process parameter combination was developed on the based of a comprehensive balance method, in which a layer thickness of 0.1 mm, a nozzle temperature of 200 ℃, a printing speed of 60 mm/s and a infill density of 30 wt % were determined. Vapor smoothing was used to further improve the surface quality of the sample, and the effects of smoothing temperature and smoothing time on the surface roughness of the sample was investigated. The results showed that the roughness decreased with increasing smoothing temperature and smoothing time. After vapor smoothing at 50 ℃ for 7 min, the surface roughness was reduced from 9.227 μm to 3.435 μm. As a result, the surface quality of the sample was improved significantly.