The invention relates to a method of differential protection in the power distribution networks based on phase difference principles. The method comprises the following steps: collecting the current and voltage signals of each loading switch; calculating phase difference between the corresponding currents at two adjacent loading switches, wherein at least one of the two adjacent loading switches accords with ΔIφmax>n·ΔIT+ΔIdz; tripping the two adjacent loading switches if the phase difference corresponding to the two adjacent loading switches being greater than a threshold then a section between the two adjacent loading switches being determined as a fault section. The method only needs to calculate the phase difference between the corresponding currents at the two adjacent loading switches, and achieves the fault determination according to the phase difference being greater than the threshold. The method has low data synchronizing requirements, and processes the fault determination according to the collected signals. The time required for the entirely determining process is short, and a fast protecting response is achieved, thus the problem of slowly protecting response in the existing relay-protection method for the power distribution networks is solved.