The invention provides a positioning method and device for fault branches of mixed multi-branch nodes of a power distribution network. The method comprises the steps that downstream branches not connected with a distributed generation are determined as passive downstream branches among a plurality of downstream branches of a bus node, and a plurality of downstream branches connected with the distributed generation are determined as active downstream branches; whether fault currents exist on the passive downstream branches or not is judged, if yes, the passive downstream branches with the fault currents are determined as the fault branches, and if not, detection currents on the active downstream branches are grouped in pairs to obtain a plurality of current groups, and the phase angle difference between the two detection currents in each current group is determined; when the absolute values of all phase angle differences do not exceed 90 degrees, upstream branches of the bus node are determined as the fault branches, and when the current groups with the phase angle absolute value exceeding 90 degrees exist, the active downstream branches where the detection currents with a high amplitude value in the current groups are located are determined as the fault branches. Consequently, positioning of the fault branches is achieved.