The basis of DED process is a sound microstructure which isdominated by the created melt pool during deposition. Melt poolformed during laser deposition is a critical factor and melt poolgeometry is a crucial factor in determining deposition quality. Tooptimize process parameters, a deep understanding of the under-lying mechanisms is beneficial. A mathematical model, as shownin Fig. 2, was developed to simulate the coaxial laser claddingprocess with powder injection, which includes laser-substrate,laser-powder and powder-substrate interactions [1]. The modelconsiders most of the associated phenomena, such as melting,solidification, evaporation, evolution of the free surface and pow-der injection. The fluid flow in the melt pool, which is mainly drivenby Marangoni shear stress as well as particle impinging, togetherwith the energy balances at the liquid–vapor and the solid–liquidinterfaces are investigated. Powder heating and laser power atten-uation due to the powder cloud are incorporated into the model inthe calculation of the temperature distribution. The influences ofthe powder injection on the melt pool shape, penetration, and flowpattern are predicted by comparison between cases with powderinjection and without powder injection. Dynamic behavior of the melt pool and the formation of the clad are simulated. The effectsof the process parameters on the melt pool dimension and peaktemperature are further investigated based on the validated model.