The invention discloses a high-voltage direct current transmission line internal fault and external fault identification method based on backward traveling waves. The high-voltage direct current transmission line internal fault and external fault identification method comprises the following steps that firstly, a voltage transformer and a current transformer installed on the rectification station line side and an inversion station line side of a direct current transmission system collect voltage and current across the two ends of a positive electrode line and voltage and current across the two ends of a negative electrode line respectively; secondly, the voltage leap amount and current leap amount of the two ends of the positive electrode line and the voltage leap amount and current leap amount of the two ends of the negative electrode line are calculated; thirdly, the voltage leap amount and current leap amount of each electrode line are transformed into corresponding line mode voltage component and line mode current component; fourthly, the voltage backward waves at the two ends of the direct current line are worked out according to the line mode voltage component and the line mode current component, and integration of backward wave amplitude values is conducted in specific time; fifthly, a specific value of the backward wave amplitude value integral on the rectification side of the direct current line to the backward wave amplitude value integral on the inversion side of the direct current line is calculated, and faults are judged according to the specific value. By means of the method, the internal faults and the external faults can be quickly and accurately recognized, correct actions can still be conducted under the high-resistance faults at the line tail end and the noise interferences, and reliability and sensitivity are high.