The present disclosure provides a method, a system and a device for determining a reference subframe. According to the embodiments of the present disclosure, with respect to one downlink CSI measurement subframe set, the UE determines a serial number of a downlink A-CSI reference subframe in the downlink CSI measurement subframe set in accordance with a predetermined rule, and determines the downlink A-CSI reference subframe in accordance with the determined serial number of the downlink A-CSI reference subframe.