In arder to improve the overlap quality of multi-beam selective laser melting, the effects of scan order of overlap area on surface appearance, metallurgical defects, tensile properties and other formability of TC4 samples have been investigated. The results show that, when the strips between adjacent layers have no relative deflection, due to the denudation of the powder, reverse order overlap causes large surface fluctuation at the overlap area using dual lasers, and is easy to cause defects of poor fusion; In order overlap can greatly eliminate surface fluctuations in the overlap area and reduce internal defects; When setting the relative strip deflection angle between adjacent layers of 67°, in order overlap can avoid internal defects and improve the surface morphology of the overlap area, and the microhardness and tensile strength are basically the same as when using reverse order. The in order overlap and the relative strip deflection between adjacent layers can improve the forming quality of the overlap area when using selective multi-beam laser melting technique.