The laser welding experiment of 304 stainless steels with powder filling is carried out, the effects of different laser welding process parameters on the cross-sectional morphology, tensile strength and fracture morphology of welding seam are studied, and the optimal process parameters are obtained. The results show that, in the experimental range, there is a positive correlation between the width of welding seam and the laser energy density. When the defocusing distance changes from zero to positive or negative value, the top welding seam width increases while the bottom welding seam width decreases. The low laser power and the zero defocusing distance can weaken the tensile strength of welding specimen. With the increase of welding speed, the tensile strength of specimens increases first and then decreases. With the increase of tensile strength, the fracture appearance is, in turn, manifested as a side-shaped cleavage fracture, a quasi river-like cleavage fracture, and an alveolate-dimpled plastic fracture. The optimal process parameters obtained from the orthogonal test are a laser power of 2.7 kW, a welding speed of 160 mm·min-1, and a defocusing ditance of +5 mm.