An electro-magnetic flow sensor, which is arranged for measuring a flow rate of liquid, includes a micro controller and a liquid flowing apparatus communicatively linking to the micro controller. The liquid flowing apparatus includes a flow chamber housing having a flow chamber for receiving the liquid therein, a magnetic source communicating with the flow chamber housing for generating a magnetic field within the flow chamber so as to allow the liquid exposing in the magnetic field, and an array of electrodes alignedly integrated with the flow chamber housing for measuring a voltage magnitude of flow generated in the flow chamber when the liquid flows within the flow chamber under the magnetic field, wherein the micro controller reads the voltage magnitude and converts the voltage magnitude into the flow data of the liquid.