Laser cladding deposition is a crucial technology for surface modification and 3D freeform fabrication, with process parameter selection significantly influencing the geometry and mechanical properties of the melt channel. This study employs the response surface analysis method to develop a mathematical model correlating process parameters—laser power, scanning speed, and wire feeding speed—with responses such as melt height, aspect ratio, dilution rate, and microhardness in an annular focus laser coaxial cladding deposition process. The results show that the scanning speed is the most significant factor affecting the height of the melt channel, aspect ratio and microhardness, and the laser power is the most significant factor affecting the dilution rate. The expected combination of process parameters was obtained by synchronous optimization method, and the predicted results were in good agreement with the experimental results, and the average relative errors of melt height, aspect ratio, dilution rate and microhardness were 8.33%, 1.67%, 2.50% and 1.71%, respectively. Using the process parameters calculated by the model, a variable-diameter thin-walled part with a height of 100 mm is formed. The dimensional accuracy of the formed parts is high, the structure is dense and uniform, and there are no obvious defects such as pores and cracks.