Smooth blasting is generally used to control tunnel formation, which requires managing the density of the line charge. Conventionally, air-spaced axial uncoupled charges are used and connected by detonating cords. However, detonating cords require a large amount, are expensive and difficult to approve, and cannot achieve uniform dispersion of charges. Currently, bottom-concentrated charging structures are used without using detonating cords in the surrounding holes of tunnel excavation, leading to serious over-excavation and under-excavation. To address this issue, a new type of energy-gathering tube has been designed. This new tube combines a PVC half tube and energy-gathering cover with a fixed ring, enabling precise control of explosive amounts, simplifying the charging process, and ensuring the stability of the entire device. It is not limited by the water environment, providing efficient energy transmission and effectively controlling tunnel over-excavation and under-excavation. To evaluate the blasting effect of the new energy-gathering tube, it was first verified through a sacrificial explosion test. The test showed that with the new tube, multiple sections of the detonated explosive can be stably transmitted at 30 cm intervals with a dosage of 60 g. Numerical simulations also demonstrated the good cutting effect of the new tube. This new energy-gathering tube was applied in the Dongshan Tunnel of the Fenyang Shilou Expressway, achieving smooth blasting without detonating cords with a line charge density of 200 g/m and a half-hole trace rate of 90%, effectively reducing over-excavation and under-excavation.