As the proportion of photovoltaic grid-connected systems increases year by year, the uncertainty of photovoltaic output and load has an increasingly significant impact on the stable operation of the distribution network. In this paper, a photovoltaic access location-capacity optimization method in distribution lines based on the quantification of photovoltaic-load uncertainty is proposed, and the uncertainty propagation of the PV load model parameters in the distribution network power flow calculation node voltage output model is analyzed. This paper proposed an improved Sobol’s method based on polynomial development to quantitatively evaluate the uncertain impact of photovoltaic load parameters, constructed a photovoltaic access location-capacity evaluation model for distribution lines based on uncertainty quantitative assessment, optimized the access capacity of nodes by using the goal function of line loss minimization, and finally verified the feasibility and effectiveness of the proposed method by improving the IEEE33 node.