The three dimensional (3D) printing has the properties of prototyping arbitrary shape of parts，which is applied widely to many fields. Path planning is one of the key techniques in manufacturing process of 3D printing. Different scanning ways have significant impacts on the prototyping precision, mechanical properties of prototyping parts and the prototyping efficiency. Aimed at these three ways separately, path planning was discussed and analyzed. Finally the importance of studies on path planning of 3D printing was pointed out.