A comprehensive three-dimensional transient model is developed for the evolution of the temperature field during the vertical wall manufacturing process using coaxial laser metal deposition (LMD), the material manufactured is directional solidification (DS) superalloy Rene80. The interaction between laser and powder during the powder falling process is simulated, and its possible effect on the temperature field of molten pool is analyzed. After that, the evolution of temperature field during the vertical wall manufacturing process is studied. By numerical simulation, the change of phase (solid/liquid, and mushy zone) and the liquid flowing are considered and the parameters are from optimized vertical wall manufacturing experiments. The results reproduce the shape changing of the molten pool and the instability of laser metal deposition process. The changing rule of temperature field is in conformity with that of real vertical wall manufacturing experiment.