With the continuous development of measurement technology, the distribution phasor measurement unit (D-PMU) has gradually matured and been applied. Reasonable configuration is of great significance for the operation monitoring of distribution network and the large-scale promotion of D-PMU. Firstly, one-shot optimal configuration method of D-PMU which meets system completely observability is presented, and the staged optimal configuration methods and planning schemes considering the measurement redundancy and unobservable depth are also provided in the paper. Secondly, considering different application scenarios, the system architecture, data flow diagram and specific module design flow chart of optimal D-PMU configuration assistant decision-making software system adapted to multi-type optimal configuration requirements are proposed, and the platform of optimal D-PMU configuration assistant decision-making for distribution network is constructed. Finally, based on a real distribution network in Guangdong, the application analysis is carried out to verify the effectiveness of the proposed method.