The invention provides an electric steam iron which comprises a water tank, a steam generating device, a bottom plate, heating elements, an electromagnetic pump and a controller. The heating elements are used for heating the bottom plate, the water tank is communicated with the steam generating device, the steam generating device is arranged on the upper portion of the bottom plate, the electromagnetic pump and the heating elements are respectively electrically connected with the controller, the water tank is communicated with the steam generating device via the electromagnetic pump, the steam generating device comprises a first steam generator and a second steam generator, and the water tank is communicated with the first steam generator via the electromagnetic pump. A method for controlling the quantity of steam of the electric steam iron includes that the quantity of water pumped by the electromagnetic pump of the electric steam iron is controlled, so that the steam generating quantity can be controlled; a set work cycle of the electromagnetic pump is 20ms, and five tap positions are set for the steam generating quantity. The electric steam iron and the method have the advantages that the steam generating quantity can be effectively controlled, so that the steam can be uniformly and stably outputted, and a suitable quantity of steam and a suitable temperature of the steam can be provided according to different clothes and fabrics.