This study addresses the issue of dispersed fatigue outcomes and anisotropic behavior in fatigue specimens produced by selective laser melting (SLM). The fatigue life (S-N) curves and microstructures of AlSi10Mg alloy, fabricated via SLM and subsequently subjected to Hot Isostatic Pressing (HIP) treatment, were compared and analyzed. The results showed that the fatigue life in X(Y) direction of AlSi10Mg is better than that in Z direction, because of the difference in the distribution direction of defects, attributed to the directional distribution of defects influenced by the SLM forming process. The fatigue strength in the X(Y) direction is 28% to 49% greater than in the Z direction under equivalent fatigue life conditions. After hot isostatic pressing treatment at 490 ℃, the difference of fatigue life in two directions is obviously decreased compared to the SLM specimens, which was due to the large size defects was closed after hot isostatic pressing treatment. Moreover, the microstructure coarsening and Si phase coarsening during hot isostatic pressing process led to the decrease of fatigue strength, especially for fatigue tests at high stress level.