The invention discloses a flotation cell liquid level automatic control device and a compensation control method thereof. The device comprises a flotation cell, a liquid level meter, gate driver, an analog quantity input module, a central processing unit (CPU) module and an analog quantity output module, wherein the analog quantity input module is connected with the CPU module; the CPU module is connected with the analog quantity output module; the gate driver is connected with the analog quantity output module; the liquid level meter is connected with the analog quantity input module; and the liquid level meter and the gate driver are arranged on the flotation cell respectively. According to the invention, a disturbance soft measurement estimation compensation technology based on a disturbance observer and a feedback control technology based on model predict control are adopted, so that the upstream ore pulp flow rate fluctuation, middling backflow ore pulp flow rate fluctuation and inhabitation performance of coupling and other disturbances among processes of each process liquid level control system of flotation in the process are overcome, the control performance of the system is improved, the requirement of a flotation process on selective cell liquid level strict control is met, the concentrate quality of the flotation process is improved, and the concentrate yield is stabilized.