The present paper investigated the influence of different solid solution time on the microstructure and micro-hardness of selective laser melting produced AlSi10Mg alloy at 535℃ solid solution temperature by using SEM, EDS and micro-hardness tester. The results showed that the microstructures of AlSi10Mg composed of nano-sized network Al-Si eutectic and the supersaturated α-Al solid solution are very sensitive to solid solution time at 535℃ solid solution temperature.After 2min of solid solution, the boundary of the molten bath and the nano-size network eutectic structure disappeared.After 5min of solid solution, the eutectic Si was obviously spherical， the size of eutectic Si increased with the prolongation of the solid solution time. With the change of microstructure, the micro-hardness of AlSi10Mg is rapidly reduced from (119±3.2)HV0.2for as-built SLM specimens before the solid solution, and with the prolongation of the solid solution time, the micro-hardness eventually stabilizes at about 57HV_0.2.