AlSi10Mg thin-walled parts were formed by laser powder deposition technology. The method of negative defocusing of powder and prolonging the interval time of cyclical cladding process were adopted to solve the problems of rough edge and collapse of cladding layer. The microstructure and mechanical properties of the thin-walled part were analyzed both in the direction of scanning and deposition. The results showed that the optimal process parameters of single-pass cladding were laser power density P=370 W/mm2, scanning speed Vs=1.2 m/min, powder feeding rate Vf=8.5 g/min. The edge collapse of thin-walled parts was improved with prolonging the interval time of cyclical cladding process, but worsened by increasing the powder negative defocusing. The microstructure of the thin-walled parts was mainly fine dendrites and a small amount of equiaxed grains in the scanning direction, but the deposition direction was mainly coarse dendrites. The hardness, tensile strength and elongation of thin-walled parts in scanning direction are 130 HV, 280.12 MPa and 12.12% respectively, which are better than those in deposition direction.