A novel trench-assisted dual-mode multi-core fiber with large-mode-field-area is proposed. The structure consists of 17 conventional cores and two air holes according to a regular hexagon, which can realize strict dual-mode transmission. The structural parameters' effect on mode transmission characteristics, mode-field-area, and bending loss are analyzed systematically. By optimizing the structural parameters, the mode-field-area of the fundamental mode can reach ${2100.619}\;{{\unicode{x00B5}{\rm m}}^2}$. The introduction of the trench with a lower refractive index than cladding can reduce the bending loss to ${9.88} \times {{10}^{- 4}}\;{\rm dB}/{\rm m}$ when the bending radius is 2.3 cm. Besides, the structural design is flexible, and the manufacturing process is simple, which has broad application prospects.