Abstract: In order to optimize the microstructure and mechanical properties of plasma arc rapid prototyped Inconel625 alloy, the alternating and cross paths were applied to forming the rectangular block sample. The effects of the two paths on the structure and properties of block samples were investigated, and the growth mechanisms of the as-deposited structures under the two conditions were analyzed. The results show that different heat input and heat dissipation directions result in different temperature gradient, and have an influence on the continuity of structure growth. The optimal forming quality and mechanical properties were obtained under the condition of alternating path. Although using the cross path can lead to the alternating structure growth, the formation of small dendrite and the disperse precipitation of Laves phase, the mechanical properties were not increased drastically because of serious element segregation, precipitation of brittleness phase and the coarsening of dendrite.