Abstract: The ongoing rise in the penetration level of large-scale distributed photovoltaics in distribution networks has imposed higher requirements for the safe and stable operation of the power grid. Transient simulation serves as an important tool for investigating the safe and stable operational technologies of power grids. However, the current transient simulation techniques face challenges in meeting the simulation timeliness and accuracy requirements of high-penetration distributed photovoltaic power grids. In view of this, we propose a large-scale distributed photovoltaic transient equivalent modeling method for distribution networks with dynamic characteristics and electrical distance taken into account. Firstly, by analyzing the distributed photovoltaic short-circuit current response theory and industry standards, a clustering method based on unit type and electrical distance is developed to divide the large-scale distributed photovoltaics into several sub-clusters. Secondly, according to the principles of "consistent types" and "power conservation", the distributed photovoltaics in the same sub-cluster are aggregated into an equivalent unit. Furthermore, by employing the equivalent lossless network construction method and node elimination method, an equivalent network is constructed between the equivalent power/load access points and the common coupling points between the distribution network and the higher-level power grid, thereby forming the final equivalent model. Finally, a simulation model is built on the PSASP7 platform to verify the effectiveness of the proposed method in this paper.