Abstract: With the development of space exploration activities, Joule heating wire additive manufacturing technology has a promising future due to its advantages such as low energy input, small equipment size, and low cost. In view of the significant impact of the surface quality of formed parts on heat input and the lack of quantitative evaluation methods for surface quality in current research, single-pass and multi-pass mathematical models were established based on experiments. Color difference diagrams of mathematical models and extracted models were comparatively analyzed. Standard deviation and root mean square values were calculated to evaluate surface quality, and experimental verification was conducted. The results indicate that the elliptical model is the most suitable for the cross-sectional contour in Joule heating wire additive manufacturing. The optimal process parameters for the best surface quality are a current of 600 A, a forming speed of 1 000 mm/min, and a center distance of 0.5 mm. By analyzing color difference diagrams and calculating standard deviation and root mean square values, the actual surface quality of formed parts can be reflected. The analysis results are consistent with the actual situation, providing important theoretical and experimental support for the development of Joule heating wire additive manufacturing technology.