The invention provides a method and a system for improving the toughness of a distribution network and a terminal device. The method comprises the following steps: acquiring a multi-energy system model and a distribution network model; determining distribution network fault scenarios satisfying preset conditions in the distribution network model by a distribution network fault probability function; establishing an unloaded cost function with the load reduction ratio of a distribution network and the load reduction ratio of a multi-energy system as optimization variables; establishing a distribution network energy storage configuration function with the configuration capacity of energy storage elements as optimization variable; optimizing the unloaded cost function and the distribution network energy storage configuration function, and obtaining the optimized configuration capacity of the energy storage elements and the load reduction ratio of the distribution network corresponding to each fault scenario and the load reduction ratio of the multi-energy system. The optimized load reduction ratio of the distribution network under different fault scenarios, the load reduction ratio ofthe multi-energy system and the optimized configuration capacity of the energy storage elements are obtained by optimizing the unloaded cost function and the energy storage configuration function of the distribution network, and thus the toughness of the distribution network is effectively improved.