In this paper, we design and demonstrate a mode (de)multiplexer using tapered couplers on a silicon-on-insulator substrate by commercial 0.18 μm complementary metal-oxide-semiconductor compatible processes. By controlling the width of a tapered waveguide, the mutual conversion between the fundamental mode in the tapered waveguide and the high-order mode in the multimode straight waveguide can be realized due to the matching of modal effective indexes. For the multiplexing and demultiplexing of the TE0, TE1 and TE2 modes, the fabricated device, which is composed of a mode multiplexer, a multimode straight waveguide, and a mode demultiplexer, exhibits crosstalk lower than -8.05 dB within a bandwidth from 1 530 nm to 1 570 nm. The crosstalk is less than -16.43 dB for the multiplexing and demultiplexing of the TE0 and TE2 modes.