The invention discloses a fertilizer distributor with an automatic feeding function, and belongs to the technical field of agricultural machinery. The fertilizer distributor comprises a machine frame, a negative pressure generating mechanism at the lower portion of the rear side of the machine frame, a material storing mechanism on the top of the machine frame, a weighing mechanism in a cavity of the machine frame, a fertilizer mixing mechanism in the cavity of the machine frame, a discharging mechanism on the front side of the machine frame, a material supplementing mechanism at the lower portion of the material storing mechanism, and an electrical control box. The fertilizer distributor is characterized by further comprising feeding mechanisms, the left side and the right side of the machine frame are each provided with at least one feeding mechanism, the feeding mechanisms are connected with the machine frame, the feeding mechanism on the left side comprises a feeding hopper supporting frame, a feeding hopper, a material bag turning frame, a turning frame driving acting cylinder and a crank arm, a weighing sensor support is fixed in the cavity of the machine frame, a discharging box fixing support is arranged on the front side of the machine frame, the weighing mechanism is fixed to the weighing sensor support, the fertilizer mixing mechanism is arranged in a cavity of the weighing sensor support, and the discharging mechanism is arranged on the discharging box fixing support. The fertilizer distributor is small in size and clean in working environment, and the fertilizer distribution efficiency, the work reliability and mixing quality are guaranteed.