We propose a novel metal-insulator-metal (MIM) waveguide mode transition scheme by the use of the abrupt junction of MIM plasmonic waveguide. Power coupling between anti-symmetric plasmonic mode and fundamental photonic mode can be easily done by reflection at the waveguide junction with an oblique MIM mode incidence due to the field intersection between those modes. With numerical simulation we find that mode conversion efficiency can be obtained up to 60% for single junction geometry, and it can be further increased up to 82% with the suppression of non-transited mode by adapting Bragg grating structure composed of periodical arranges of MIM junctions.