<p>Laser powder bed fusion (LPBF) has attracted increasing attention owing to its advantages in fabricating complex-shaped structure in aerospace, medical, and automobile fields. However, pore defects in the built part may weaken its mechanical properties. Pore defects are typically classified into three types: lack of fusion (LOF), gas pores, and keyhole pores. In this study, we used in-situ re-scan to decrease pore defects and then investigated the influence of the re-scan strategy on decreasing pores. Two scan strategies were used in this study, including meander scanning strategy (M) and chessboard scanning strategy (C). The results have shown that under optimized process parameters, the relative densities of the M and C samples were 99.916 and 99.802%, respectively. The M + M and C + C samples achieved relative densities of 99.996 and 99.983%, respectively. The C + M sample reached a relative density of almost 100%, with no porosity defects detectable by Micro-CT. M + M (the former for LPBF, the latter for re-scan) strategy mainly decreases gas pores and keyhole pores due to the stable keyhole and molten pool of M re-scan. C + C re-scan strategy is good at eliminating LOF defects, which underwent multiple melts by C re-scan. More importantly, C + M re-scan strategy effectively decreases all the three types of pores. This study presents a distinct relationship between scanning strategy and pore defects, as well as an effective approach to decrease pore defects by laser re-scan with optimized scan strategy.</p>