Abstract: The integration of new high-permeability distributed energy into the power grid has increased the demand for flexibility in the distribution network owing to the randomness and volatility of its output. A method for improving the flexibility of distribution networks that considers the complementary characteristics of soft open point（SOP） and smart load（SL） is proposed. First, the flexibility characteristics and mathematical models of the SOP, SL, controllable DG, and flexibility evaluation indicators were established from two aspects: node flexibility adaptability and the load margin of lines containing the SOP. Second, we constructed an objective function that considers the operating costs, voltage quality, and flexibility indicators, striving to achieve optimal economic performance while minimizing flexibility gaps and voltages exceeding the limits. Simultaneously, a reconstruction whale optimization algorithm（Re-WOA） was proposed to solve the optimization model, and two improved search predator strategies were introduced in the algorithm. The SL load balancing degree during the search phase was balanced using the SL capacity margin index. Finally, the optimization effect of the model on the distribution network and the effectiveness of the proposed Re-WOA were verified using an improved IEEE33 node system.