The location of incremental distribution network connected to public power grid affects its investment economy and the security and stability of main network. To solve this problem, firstly, this paper expounds the randomness of distributed generation output and load in incremental distribution network, takes into account the economy, reliability and stability of incremental distribution network access, and establishes the location planning model and evaluation model of incremental distribution network from the perspective of incremental distribution network and main power grid. Secondly, the opportunity constrained programming is used to deal with the uncertainty of source and load. On this basis, the opportunity constrained programming is linearized by decomposition method. Finally, the simulation experiment of the improved IEEE 33 node system is carried out, and the location planning results of incremental distribution network and the evaluation of stock distribution network are analyzed. The results show that the investment users of incremental distribution network prefer to choose the closer tie line to access, so as to save the line erection cost and improve the power supply reliability, while the main power grid is more expected to improve the voltage quality from the end of the distribution network.