The invention discloses a reactive switching optimization simulation system for a transformer substation. The reactive switching optimization simulation system comprises a data acquisition module, a calculation module, an optimization module and an executing module, wherein the data acquisition module is used for forming an operating mode before switching according to a combination of basic parameters and a power flow mode of equipment in the transformer substation, and obtaining operating mode data before switching; the calculation module is connected with the data acquisition module and used for obtaining a calculation result of a reactive state variable according to the operating mode data before switching; the optimization module is connected with the calculation module and used for performing switching optimization according to the calculation result of the reactive state variable, and determining reactive compensation capacity in the transformer substation; and the executing module is connected with the optimization module and used for performing verification on reactive exchange capacity in medium-voltage side voltage changes under a set reactive compensation state according to the reactive compensation capacity in the transformer substation. The invention also discloses a reactive switching optimization simulation method for the transformer substation. The reactive switching optimization simulation system and method are low in reactive exchange power and good in control effect.