Laser powder bed fusion (LPBF) has emerged as one of the primary metal additive manufacturing technologies for the production of complex-shaped parts. However, it has always been difficult for LPBF to improve build efficiency while preserving high forming quality. In this study, a novel scanning strategy which uses high-power laser(s) with large spot sizes to scan the entity and adopts low-power laser(s) to scan the contour is investigated. The variation of spot size is achieved by shifting the focal plane through a dynamic focusing unit. Block Inconel 718 alloy specimens prepared using this novel scanning strategy exhibit smaller average roughness on both the side surface (9.3 ?m) and top surface (11.4 ?m), compared with specimens fabricated entirely with high-power laser. Besides, the dimensional accuracy and surface quality of inclined structure, circle structure and thin-wall structure come close to the level of structures built by low-power LPBF. Although some pores are found to be induced at the overlap regions between the entity and the contour, the mechanical properties are barely affected. The optimal performance with ultimate tensile strength, yield strength and total elongation of 1128 MPa, 825 MPa, and 29% is comparable to the current first-class level. But its build efficiency has nearly doubled the level obtained in traditional low-power LPBF. Moreover, this raise is more pronounced in a dual laser system by utilizing the unique scanning strategy without compromising forming quality. The prevent study offers a possible solution for ensuring both build efficiency and forming quality.