Abstract: In order to avoid defects such as overburning and collapsing at the boundary of laser cladding layer, difference of heat dissipation at different positions of the substrate was analyzed based on the theory of heat conduction. The influence of scanning path on temperature distribution was studied by numerical calculation. With the parameters of laser power 1000W, scanning speed 5mm/s, powder feeding quantity 9.15g/min, scanning interval 1.5mm and substrate size 40mm×30mm×7mm, molten pool temperature of boundary under the same direction cladding and different side cladding is about 300℃ and 500℃ lower than that under different direction cladding and the same side cladding respectively. Overburning and collapsing regions under different direction cladding and the same side cladding are predicted and experimentally verified. The results show that the scanning path has a great influence on the overburning and collapsing of boundary. The same direction cladding and different side cladding can improve the cladding quality of boundary without changing machining efficiency, material utilization ratio and the rationality of process parameters. Different side cladding can balance the relationship between heat accumulation and heat dissipation better, which can refine the grain of boundary, make internal microstructure uniform and increase the performance of cladding layer. This study is helpful to improve the quality of laser cladding layer.