A bending-resistant multimode fiber with a large core diameter and a high numerical aperture, comprising: a core; and a cladding surrounding the core; wherein the radius R1 of the core is in a range of 28 to 50 μm, the refractive index profile n(r) of the core has a parabolic shape according to the following exponent function: n 2 r = n 1 2 ⁢ 1 - 2 ⁢ Δ ⁢ 1 % max ⁢ r R ⁢ 1 α for r < R1 with r being the distance from the central axis of the fiber, the exponent α being a parameter in a range of 1.9 to 2.2, Δ1%max being the maximum relative refractive index difference between the core and the cladding; the maximum relative refractive index difference in the core Δ1%max is in a range of 2.15% to 2.5%; and the cladding comprises an optional inner cladding and a trench cladding, and an outercladding disposed from the inner to the outer in sequence, wherein the inner cladding has a radius R2 in a range of 28 to 55 μm and a relative refractive index difference Δ2% in a range of -0.1% to 0.1%, and wherein the trench cladding has a radius R3 in a range of 40.3 to 60 μm, and a relative refractive index difference Δ3% in a range of -0.15% to -0.8%; the expression "relative refractive index difference" of a part of the fiber, i.e. Δ1%max, Δ2% and Δ3%, Δ4% referring to the following formula: Δ i % = / 2 ⁢ n i 2 n i 2 - n 0 2 × 100 % ≈ n i - n 0 n 0 × 100 % where n i and n 0 are respectively the refractive index of the corresponding part of the fiber and of pure silica glass at a wavelength of about 850 nm. Wherein it has a numerical aperture in a range of 0.304 to 0.33. a core; and a cladding surrounding the core; wherein the radius R1 of the core is in a range of 28 to 50 μm, the refractive index profile n(r) of the core has a parabolic shape according to the following exponent function: n 2 r = n 1 2 ⁢ 1 - 2 ⁢ Δ ⁢ 1 % max ⁢ r R ⁢ 1 α for r < R1 with r being the distance from the central axis of the fiber, the exponent α being a parameter in a range of 1.9 to 2.2, Δ1%max being the maximum relative refractive index difference between the core and the cladding; the maximum relative refractive index difference in the core Δ1%max is in a range of 2.15% to 2.5%; and the cladding comprises an optional inner cladding and a trench cladding, and an outercladding disposed from the inner to the outer in sequence, wherein the inner cladding has a radius R2 in a range of 28 to 55 μm and a relative refractive index difference Δ2% in a range of -0.1% to 0.1%, and wherein the trench cladding has a radius R3 in a range of 40.3 to 60 μm, and a relative refractive index difference Δ3% in a range of -0.15% to -0.8%; the expression "relative refractive index difference" of a part of the fiber, i.e. Δ1%max, Δ2% and Δ3%, Δ4% referring to the following formula: Δ i % = / 2 ⁢ n i 2 n i 2 - n 0 2 × 100 % ≈ n i - n 0 n 0 × 100 % the radius R1 of the core is in a range of 28 to 50 μm, the refractive index profile n(r) of the core has a parabolic shape according to the following exponent function: n 2 r = n 1 2 ⁢ 1 - 2 ⁢ Δ ⁢ 1 % max ⁢ r R ⁢ 1 α for r < R1 with r being the distance from the central axis of the fiber, the exponent α being a parameter in a range of 1.9 to 2.2, Δ1%max being the maximum relative refractive index difference between the core and the cladding; the maximum relative refractive index difference in the core Δ1%max is in a range of 2.15% to 2.5%; and the cladding comprises an optional inner cladding and a trench cladding, and an outercladding disposed from the inner to the outer in sequence, wherein the inner cladding has a radius R2 in a range of 28 to 55 μm and a relative refractive index difference Δ2% in a range of -0.1% to 0.1%, and wherein the trench cladding has a radius R3 in a range of 40.3 to 60 μm, and a relative refractive index difference Δ3% in a range of -0.15% to -0.8%; the expression "relative refractive index difference" of a part of the fiber, i.e. Δ1%max, Δ2% and Δ3%, Δ4% referring to the following formula: Δ i % = / 2 ⁢ n i 2 n i 2 - n 0 2 × 100 % ≈ n i - n 0 n 0 × 100 % where n i and n 0 are respectively the refractive index of the corresponding part of the fiber and of pure silica glass at a wavelength of about 850 nm. Wherein it has a numerical aperture in a range of 0.304 to 0.33.