The invention provides a device for mixed injection of fiber airflows. The device comprises a to-be-mixed fiber material supply device and a melt-blow device, wherein the to-be-mixed fiber material supply device comprises a first roll, a second roll and a transportation air flue; the first roll and the second roll are arranged in parallel along the longitudinal direction of the transportation air flue; a notch is formed in the transportation air flue; the second roll partially extends into the transportation air flue from the notch, so as to bring a to-be-mixed fiber material into the transportation air flue; the melt-blow device comprises a spinneret die head; the spinneret die head comprises a spinneret plate and a spinneret plate cover; along the longitudinal direction of the transportation air flue, the first roll, the second roll and the spinneret die head are arranged in sequence; the first roll and the second roll are located below the transportation air flue; and the spinneret die head is located above the transportation air flue. By adoption of the device for mixed injection of fiber airflows, the effective stroke of the to-be-mixed fiber material in the air flue is greatly shortened, the mixing uniformness of the to-be-mixed fiber material and melt-blow fiber is effectively improved, and the finished product quality is improved.