A novel accurate location of faults on power transmission line with two-end phasor measurement used in differential protection device is proposed. The new algorithm may solve the shortages such as complex calculations of calculating the hyperbolic functions, large amount of calculation with the Newton-Raphson iteration and binary search and needing accurate line parameters. The algorithm is simple in principle, it can calculate the accurate parameters of the transmission line, coefficient of asynchronous sampling and fault distance through simple complex operation. The algorithm uses the positive sequence fault component to calculate the fault distance, is able to adapt to all type of fault, and the calculation results have fast convergence and do not influenced by the transition resistance.