Focused on the problem of complex modeling and solving process in Distributed Generation (DG) planning at present, the concept of DG tolerant permeability ratio in distribution network is proposed. The influence of characteristic parameters on tolerant permeability ratio is analyzed. A novel method of DG planning is put forward based on tolerant permeability ratio in 10 kV distribution network. Firstly, the 10 kV distribution lines are classified according to their own electrical characteristics. Secondly, the base-state models of each type of lines are established. Thirdly, the tolerance permeability ratio of 10 kV distribution lines in extreme parameter situation are calculated through base-state model, within the range of characteristic parameters among similar lines. Finally, the tolerance penetration ratio recommended tables of each type of lines are made to guide DG planning in distributed network. The validity and correctness of the proposed method are verified by the results of calculation case. This work is supported by National Natural Science Foundation of China (No. 51777077).