The invention discloses a real-time monitoring method and system for line loss rate. The real-time monitoring method comprises the steps of pre-establishing a real-time data acquisition interface in an electric energy metering automatic system; obtaining real-time electric energy data through the real-time data acquisition interface; calculating the corresponding real-time line loss rate according to the real-time electric energy data; and judging whether the real-time line loss rate is within a preset normal range of the line loss rate or not, and if so, generating the corresponding abnormal line loss warning information. Therefore, the current real-time electric energy data can be obtained through the real-time data acquisition interface established in the electric energy metering automatic system; then the corresponding real-time line loss rate can be calculated according to the real-time electric energy data; next, whether an abnormal line loss phenomenon exists in the current power grid or not can be rapidly obtained by judging whether the real-time line loss rate is within the preset normal range of the line loss rate or not; and due to the real-time monitoring method, the acquisition period of the line loss rate is greatly shortened, so that the abnormal line loss phenomenon existing in the power grid can be found in time.