Abstract: In this paper, a titanium alloy test block with roughness ranging from Ra0.5 to Ra9.5 was designed to solve the problem of excessive interference of fluorescent background in the detection of defects related to the rough surface of molded parts by laser selective melting additive manufacturing. An artificial defect array with a diameter of 100 μm~500 μm and a depth of 100 μm~500 μm was prefabricated by laser drilling. The display characteristics of surface hole defects under different surface roughness were studied by various processes such as washing and post-emulsification. The influence of different surface roughness of laser selective melting additive manufacturing titanium alloy on the permeability detection of small defects was mastered, and the permeability detection characteristics and detection capability of laser selective melting additive manufacturing surface defects were determined.