The utility model discloses a failure detection device for a power transmission line, which solves the problems of unavailable detection of grounding, short circuit and open circuit failures and relatively low use reliability of the conventional failure detection device for the power transmission line. The detection device consists of a plurality of groups of failure information acquisition devices, failure information transmitting devices and a data processing device, wherein each group comprises three failure information acquisition devices; the failure information transmitting devices correspond to each group of failure information acquisition devices, receive failure information sent by each group of failure information acquisition devices and forward the received failure information through a global system for mobile communication (GSM) network; and the data processing device receives and processes the failure information transmitted by the failure information transmitting devices through the GSM network and consists of a computer and an information receiver which is connected with the computer. The failure detection device can transmit the line state of each monitoring point to a monitoring center under the conditions of a short circuit failure, a grounding failure, a generation failure and power failure occurring on the line; and after relevant data is received, the monitoring center can alarm and display within certain seconds and a failure generating location is positioned between two monitoring points.