The invention provides a device and a method for increasing a gap distance and improving a smooth blasting effect. The device comprises a donor explosive cartridge energy gathering device, a receptorexplosive cartridge energy accumulation device, a slender bamboo chip and a support cushion block, wherein the donor explosive cartridge energy gathering device comprises a sleeve pipe body; a first groove and a second groove are symmetrically formed in the sidewall of the sleeve pipe body in the length direction; the sections of the first groove and the second groove are V-shaped; metal energy gathering caps are connected to the two ends of the sleeve pipe body; the metal energy gathering caps are detachably connected with the sleeve pipe body; the metal energy gathering caps are sunken to beconical; and lead grooves are formed in positions close to the metal energy gathering caps, of one end of the sleeve pipe body. The device and the method solve the problems of high blasting cost caused due to that a detonating fuse is adopted for detonating, and high possibility of a miss-fire accident caused due to a blasthole groove effect, in an existing tunnel blasting method, and are capableof remarkably improving the smooth effect of contour forming for a tunnel section.