Abstract: Due to low laser absorption rate and high thermal conductivity, the properties of micro-structure of aluminum alloy formed by laser melting deposition (LMD) are greatly affected by temperature field. In order to analyze the temperature field of annular beam LMD aluminum alloy molten pool and its’ influence, optimize the forming quality and the performance of forming parts, the Ar-supplied protective LMD technology was used, the AlSi10Mg aluminum alloy forming experiment was carried out. The shape and change of the temperature field of molten pool were systematically analyzed, as well as the influence mechanism of the temperature field on the forming quality, porosity, the properties of micro-structure. The results show that the overall shape of the temperature field of the ring beam LMD aluminum alloy molten pool is "half crescent" with the opening in the scanning direction. With the increase of laser power, the temperature field shape becomes more and more sharp, and its high temperature rate, temperature gradient and average temperature also increase accordingly. The increase of the average temperature of the temperature field can increase the laser absorption rate, coarsen the micro-structure and reduce the micro-hardness. The temperature field affects the porosity rate of the formed part significantly and thus changing the tensile properties. Finally, when the average temperature is 857.7 ℃, the porosity rate is reduced to 2.1%, and the tensile strength is 305.6 MPa, and the elongation rate is 5.7%, which is 52.5% higher than the casting. It provides theoretical guidance for LMD aluminum alloy temperature field and properties of micro-structure control.