Abstract: 316L samples were formed by selective laser melting technology.The effects of layer rotation angle on the pore distribution and porosity were studied by changing the printing strategy, and using ANSYS APDL numerical simulation, the causes of the pores were analyzed from the changes of molten pool characteristics.The results show that with the excess heat accumulation, the size, maximum temperature and liquid phase time of the molten pool increase gradually, and the cooling rate of the molten pool decreases, resulting in the formation of pores.With the increase of layer rotation angle, pore distribution is uniform and the porosity decreases.Laser remelting and interlayer rotation scanning are beneficial to overlap the contour of molten pool and reduce the influence of powder spheroidization, and effectively reduce the porosity.