A power distribution network investment method based on reliability planning includes the steps of determining a planning area, analyzing weak links of a power distribution network, setting reliability targets by comparing power supply zones, arranging planning projects according to the weak links of the power distribution network, calculating scheme reliability of the planning projects, judging whether the scheme reliability meets the set reliability targets or not, determining a scheme with the lowest unit investment, determining the planning projects and the like. The power distribution network investment method based on reliability planning has the advantages that the different reliability targets are set according to different zone characteristics, the projects of the power distribution network are arranged reasonably according to investment sensibility of different optimization measures of the weak links of the power distribution network, the investment orientation is controlled, the pertinence and effectiveness of investment of the power distribution network are increased, and therefore the power distribution network investment method based on reliability planning is more scientific and comprehensive. The power distribution network investment method based on reliability planning provides beneficial reference for investment of the power distribution network by power distribution network planning personnel, provides powerful technical support for later power distribution network planning work and is easy to master and operate, and people can easily understand setting of the reliability targets of the power distribution network, ranking of the planning projects and other aspects.