This paper systematically describes the problems and challenges of 5G private network and its application，and points out the main reasons why 5G private network fails to achieve large-scale application in the industry. The goal of 5G private network is to build a flexible，scalable，reliable，secure and intelligent network. Therefore，it is proposed that the key to build 5G private network lies in the ability to build basic network elements in the whole network process，including network slicing，network reliability，connection flow，security and edge computing service capabilities. The 5G private network with the above capabilities can achieve any form of flexible networking，and can provide a unified standardized interface to meet the upper application services through the capability platform. Finally，the exploratory applications and prospects of some typical scenarios of 5G private network are given.