This paper proposes a multi-objective coordinated planning method for flexible interconnected distribution network. By comprehensively considering investment and operation cost of soft open point (SOP), network losses, and load loss, a multi-objective optimization model is constructed. The model incorporates power flow constraints and is reformulated using second-order cone programming (SOCP) with linearization techniques to address nonlinearity and improve computational efficiency. In the planning process, all possible branch fault scenarios are traversed to calculate network losses and load losses, thereby obtaining the optimal planning solution. The proposed approach is applied to the IEEE 33-bus distribution system for validation. The proposed method is validated through comparative analysis between the traditional tie-switch case and the SOP-based case. Comparative results indicate that SOP-based planning effectively enhances outage recovery and improves voltage quality, while maintaining economic viability.