A method for switching between different RATs is provided. The method is executed by a mobile communications device camping on a first cell using a first Radio Access Technology (RAT). The method includes: determining, by a controller of the mobile communications device, a data transmission rate of the mobile communications device in the first cell; sending, by the controller, a first measurement report according to the determined data transmission rate, wherein the first measurement report is intended to trigger a handover procedure initiated by the first cell or to release a radio resource control (RRC) connection; and switching, by the controller, to camp on a second cell using a second RAT via the handover procedure or a local releasing procedure after the sending of the first measurement report.