The invention discloses a flax wet-spun blended yarn comprising flax roves, wherein the flax roves comprise first flax roves and second flax roves, the number difference of the first flax roves and the second flax roves is not larger than 1.2, polyester filament yarns are added in the flax roves to form a flax wet-spun blended yarn main body, and the flax wet-spun blended yarn main body is in an S direction of twist. The invention also discloses a preparation method of flax wet-spun blended yarn. The invention also discloses a spinning frame for preparing the flax wet-spun blended yarn. The preparation method of the flax wet-spun blended yarn comprises the steps of: threading the polyester filaments with the first flax roves and the second flax roves to form the flax wet-spun blended yarn, wherein the flax wet-spun blended yarn is in the S direction of twist. The flax wet-spun blended yarn disclosed by the invention has the advantages of being gorgeous, glossy, stiff and smooth and durable, and needing no ironing.