Selective laser meling(SLM) can be used for rapid forming of metal parts with arbitrary structure, but the internal structureand material properties of the parts are significantly different from traditional parts. The elastic constants and their distribution in differentdirections of SLM 316L stainless steel parts are characterized based on a dual-mode ultrasonie transducer. Firstly, a measurement systemof ultrasonie elastic constant distribution is built by designing and fabricating a high-performanee dual-mode ultrasonic transducer. Thelongitndinal wave and two orthogonal shear wave velocities of 316L stainless steel samples prepared by SLM are measured suecessively,and the elastic modulus and Poisson's ratio in different directions at the same position are obtained. Through the meusurement of soundvelocity in different forming directions, it is found that SLM parts show significant diference in the melted layer in the z direction ofstacking, showing obvious anisotropy. The distribution of elastic constants in the y-= plane shows that Young's modulus Ers is greaterthan Enz, and Poisson's ratio aris is less than Gris, and each melted layer of the part has similar elastic constant distribution rule. Inaddition, the influences of msin process parameters such as seanning speed and hateh space on the elastie constants are also discussed.The effeetive nondestructive characterization of elastie constants of selective laser meling parts will provide a technical basis for intemalquality control and process improvement of additive manufacturing parts.