In order to study the optimal process parameters of laser welding of Q235/316 dissimilar thin steel plate, the laser tailor welding test was carried out by Nd: YAG pulsed laser. Five factors and four levels of orthogonal experiments were designed to study the effects of various process parameters on elongation and tensile strength after fracture. The welding parameters were optimized by range analysis method, and the comprehensive optimal parameter combination was found by multi-objective fuzzy comprehensive evaluation method. The results show that the factors affecting the elongation and tensile strength of the process parameters are defocus amount>pulse width>frequency>scanning speed>current, and the defocusing amount D is the most important influencing factor of welding quality; The optimal combination of the rate is A4B4C4D4E1, and the optimal combination of tensile strength is A1B4C3D4E2. After the fuzzy comprehensive evaluation, the integrated optimal process parameters are current P of 150 A, pulse width T of 2.4 ms, frequency f of 22 Hz, defocusing. The quantity h is -17 mm and the scanning speed v is 250 mm/min; after optimization, the welding quality of the sample is stable and the mechanical properties are good.