Service brake valve and system, control method and electric loader

The invention relates to a service brake system, and aims to solve the service brake problem of an electric loader. The service brake valve, a service brake system, a control method and the electric loader are provided, wherein the service brake valve is characterized by comprising an oil inlet, an oil outlet and an oil return port, and further comprising a two-position three-way electric proportional pressure reducing valve and a two-position three-way electromagnetic valve; a first oil port of the electric proportional pressure reducing valve is in communication with the oil inlet, a second oil port is connected to a first oil port of the two-position three-way electromagnetic valve, and a third oil port is in communication with the oil return port; and a second oil port of the two-position three-way electromagnetic valve is in communication with the oil outlet, and a third oil port is in communication with the oil inlet. The service brake valve is an electric control valve and is controlled by the controll