This paper analyses the mechanism of dynamical condensation of the laser molten pool and balling effect. Direct metal laser sintering process was used to carry out series of sintering experiments of Fe powder and Ni45 alloy powder. The result indicated that it was easy to appear warpage deformation and balling effect during direct sintering metal powder, and the formation quality of the parts was bad, though getting multi-layers sintered part by adjust process parameters, the density was low. But by using appropriate process parameters, much densification sintered parts by sintering small grain size Ni45 alloy powder can be obtained, its microstructure was fine and uniform, surface smooth and bonding firmly with substrate.