“Morphology self healing effect”is an important phenomenon that may happen in the direct laser melt forming process, which can adjust the process parameters of itself and control the multi- level melting channel accumulation surface from a bump unstable state to a stable state in the process of accumulation. By adopting the new process of“hollow laser, internal laser powder feeding”, adjusting the ring laser defocused amount can effectively result in self healing effect of melting channel bump defect. The impact of laser defocused amount on monolayer thickness accumulation is theoretically analyzed and resulted in a curved diagram between laser defocused amount and monolayer thickness accumulation and it has been tested as accumulate multiple thin wall samples in 304 stainless steel substrate with“fence bulge”. At the same time, the thin wall width, microstructure and thickness have been analyzed by venire caliper, scanning electron microscope and micro hardness instrument. The study has shown that there is a significant impact of different laser defocused amounts on the self healing capabilities. When the defocused amount is 0~-3 mm, the surface topography of the thin wall is undulating, and“the self healing phenomenon”has not been shown. While the defocused amount is -3 mm~-5 mm, the thin wall undulating surface will become smooth gradually in several levels, and the“self healing phenomenon”has been verified. The thin wall by self healing repair combines well with the substrate metallurgy and the width slightly changing. The structure is dense and uniform, and the hardness value from the wall top to the substrate increases slowly.