The invention discloses a power distribution network fault diagnosis system and method based on a CIM model. Secondary diagnosis and judgment are performed on a result of fault positioning, thus the accuracy of power distribution network fault diagnostic analysis can be further improved, and at the same time, RSA encryption and a digital signature algorithm are utilized to perform confidential treatment on data transmitted through an interface, thereby improving information security and confidentiality. Based on an IPX/SPX network high-speed transport protocol, data transmission efficiency is improved, and high efficiency of big data transmission is satisfied. Through extension of a distribution network emergency maintenance platform in a medium- and low-voltage power supply path fault, fault control is practically performed on an overall power supply path of the distribution network, thereby facilitating safety command by a regulation and control center and on-site interaction, and improving the lean level of emergency maintenance.