The invention relates to an overload protection device and an overload protection method for a valve actuator and aims to solve the problem that a conventional like product is not good enough in structural design. The overload protection device is characterized in that after an oil-water filter and a manual bi-directional valve inside the tank body of the overload protection device are connected in sequence, the manual bi-directional valve is respectively connected with forward and reversal rotating overload protecting components through two pipelines, and a pressure control valve, a flow adjusting valve and a three way switch valve inside the each set of the overload protecting component are connected in sequence, one pipeline of the pressure control valve is connected with one pipeline of the three-way switch valve through an auxiliary gas pipe, and the pressure control valve and the flow adjusting valve are respectively provided with a control pressure gauge and a flow pressure gauge, and the oil-water filter is provided with a filtering pressure gauge and a pressure regulating valve. The two ends of the connecting seat of the pressure control valve are respectively connected with the flow adjusting valve and the manual bi-directional valve through air pipes of the pipelines, three through holes are formed in the seat body of the connecting seat, and are respectively connected with the control pressure gauge, a voltage-stabilizing valve and the flow adjusting valve. The overload protection device provided by the invention is suitable for being used as an overload protecting device for an air actuator in a pneumatic valve.