The thermophysical process of laser deposition fabrication was combined with the geometric characteristics of thin-walled parts, a prediction model of deposition width was established based on the energy conservation relationship in the interlaminar deposition process. The model elaborates the relationship between deposition width and laser power, scanning speed, and powder feeding rate. Several groups of samples were prepared by Ti–6Al–4V (TC4) powder deposition to verify the prediction model. The results show that the model can accurately predict the deposition width of thin-walled parts under different process parameters, which improves the accuracy of experimental accuracy and efficiency. This results lays a theoretical foundation for the forming accuracy control of laser deposition manufacturing process in small molten pool.