The loop closing operation of a distribution network may generate a larger steady-state current and impulse current. To establish the equivalent model of the loop closing operation to calculate the current and analyze the feasibility is the basis of ensuring the safe and stable operation of a power grid. For the problem of large errors in existing loop closing models and current calculation methods, this paper proposes a loop closing circuit equivalent model that considers main network, feeder multi-load and transformer equivalences. Second, it combines a superposition theorem, a forward and backward substitution method and the Newton Raphson method to calculate the loop closing steady-state current. This can solve the problem that iteration may not converge. Then, it analyzes the loop closing transient process based on the Thevenin equivalent circuit and derives the expression for the loop closing impulse current by using the optimum frequency method. Finally, the simulation model is built based on PSCAD software, and it is concluded that the error of the calculation result of the proposed method is the smallest. The accuracy and superiority of the proposed equivalent model and calculation method are verified. This is of significance for the safe loop closing operation.