Network structure, load distribution and its growth mode are the main factors affecting the load supply capacity of distribution network. Most traditional evaluation methods working from the perspective of planning have the disadvantages of inconsistent load growth with the reality and ignoring the dynamic adjustment of grid. This paper proposes a load supply capacity evaluation method considering the mode of actual load growth from the perspective of actual load change. Firstly, load forecasting is conducted through the growth of existing load points and the expansion of large consumer, and the load growth mode is determined in combination with sequence operation theory. Secondly, an optimization model of power supply potential that takes into account network reconfiguration and large user access is proposed to prevent the premature appearance of power supply bottlenecks during load growth. Finally the load supply capacity by the improved repeat power flow is obtained. According to the case study on the PG&E 69-bus system with the first scenario of natural load growth and the second scenario of natural load growth with large consumer expansion at the same time, the practicability and validity of the method are demonstrated.