Loop closing operation is an important measure for the power dispatching center to adjust distribution network operation mode without power interruption. A new distribution network reconfiguration model is developed with the loop closing operation constraints taken into account. This model takes the minimum of network losses as objective function and considers the constraints of node voltage and line power in both normal and loop closing operating modes. The greedy randomized adaptive search procedure algorithm is adopted to solve the new model. The distribution network power flow calculation method based on the Thevenin theorem is used to validate the safety of loop closing operation. The detailed loop closing operation procedure that can be realized without power interruption is obtained by the method proposed. The numerical results in two test systems have validated the correctness and effectiveness of the proposed new model and algorithm.