Abstract: This paper presented a DC arc fault location method of the cable by natural frequency. Firstly,a transient voltage information is recorded at the first end of the transmission line after an arc fault occurs. For series arc fault,by extracting the data after circuit breaker action. For parallel arc fault,by extracting the data before circuit breaker action. Then the principal component of natural frequency can be chosen. Finally,a specific formula d = v/（2f） is used to calculate the distance of fault points whatever series or parallel arcs distance. Compared with the traditional traveling wave method,it has the advantages of simple calculation,high accuracy and low cost. The reliability and practicability of the method are proved by circuit model simulation and experiment test with a low voltage DC transmission platform. The test results show that the distance measuring error is less than 6%.