Abstract: The modeling and analysis of the cross-sectional profile of the weld bead provide the necessary topography data for slicing, path planning and process automation in wire and arc additive manufacturing process. MATLAB is used to develop an adaptive fitting program based on image processing and curve fitting, which can adaptively select a suitable fitting model function among the semi-elliptic function, arc function, cosine function and parabolic function. Based on this program, the distribution of the best mathematical model function of the single-layer single-pass weld bead profile in the feasible region of welding parameters, and the best model function of the weld bead profile on different layers in the multi-layer single-pass deposition are studied and analyzed. The results show that the adaptive fitting program has good accuracy in fitting the profile curve of the weld bead section; in the feasible region of deposition parameters, the profile of the single-layer single-pass weld bead can be represented by a semi-elliptic function or a cosine function model; for multi-layer single-pass stacking, the semi-elliptic function model has the highest fitting accuracy to the top profile of the weld bead.