The invention provides a line fault detection method based on a carbon fiber conductor. The method comprises the following steps: obtaining parameters of a carbon fiber conductor line high-voltage switch, and recording closing and opening coil current of the high-voltage switch; by analyzing waveform of the closing and opening coil current and stroke curve in the switching actions, judging whether switch electrical and mechanical characteristics of the high-voltage switch are normal; obtaining a real-time temperature value of a transformer through a transformer intelligent measurement and control instrument, and comparing the obtained temperature value with a preset value of the temperature corresponding to the model of the transformer; and obtaining a conductor sag, calculating the conductor temperature according to the conductor sag, and judging the operation condition of the current line with the obtained environment parameters being taken into consideration. The method realizes on-line automatic detection and control of the operation condition of the power transmission line.