Electron Beam Selective Melting (EBSM) is an additive manufacturing technology that directly fabricates parts from metal powders in a layer-by-layer fashion. The material molten time, which equals the total time that material keeps molten during scanning, is selected as an indicator for evaluating the effects of process parameters on material deposition. A finite elements model was established to simulate the molten time distribution within the scanning area for various parameters. Samples were fabricated using the same parameters in simulation. It’s found that there is a strong relation between the molten time and material deposition behavior. Appropriate material molten time results in a dense and flat surface. Too little material molten time leads to a non-dense surface and internal pores, and too much material molten time leads to a distorted surface and coarsened microstructures. The material molten time increases with the increase of beam current and with the decrease of scanning velocity and length of scanning line. An optimized process which aims to obtain appropriate and homogeneous molten time within the scanning area is also developed to improve the deposition quality.