The invention discloses a DC transmission line fault ranging method based on dual data sources, comprising the following steps: carrying out conventional sampling and high-speed sampling on the voltage and current on both sides of a line; carrying out ranging computation on conventional sampling data in a time-domain method according to a Bergeron model to get the voltage uk(x, t) at a position which is x from a measuring end at time t and the voltage um(x, t) at a position which is x from an opposite end at the time t, and getting a possible fault distance x when the two voltage values are equal; carrying out ranging computation on high-speed sampling data in a single-ended travelling wave method to get possible fault points; and removing fault points according to the results of step B and step C, and getting the position of a final fault point. The traveling wave method and the time-domain method are combined. The analysis result of the time-domain method is verified using the analysis result of the traveling wave method. Thus, ranging is more accurate and reliable.