The invention discloses a blocking pilot protection method suitable for a closed loop operation cable distribution loop network. The positive sequence fault component power directional characteristics of two inlet wires of a loop network cabinet when different locations have faults are analyzed, the loop network cabinet is divided into three states, and the unified blocking signal transmitting rules are prescribed. After the faults occur, the sudden change of current exceeds the preset threshold of STU installed in the loop network cabinet, and protection is started and automatic time checking is performed. Then each STU judges the state of the loop network cabinet and receives and transmits the blocking signals according to the prescribed rules. If the STU does not receive the blocking signals within the prescribed time period, tripping signals are transmitted to isolate the faults; and if the STU receives the blocking signals within the prescribed time period, the corresponding circuit breakers are blocked and protection automatically returns. According to the method, the exchange rules of blocking information between the adjacent STU are established according to the state of the loop network cabinet so that rapid and accurate locating of the feed line fault sections can be realized and the fault processing speed can be enhanced.