The integration of renewable energy into power plants leads to high reactive power consumption in the auxiliary power system, which not only impacts the reactive power output to the external system but also lowers the operational voltage range of the auxiliary power system and increases active power losses within the system. In order to improve the economic benefit of power plant, a reactive power optimization method considering renewable energy access is proposed, and a multi-objective reactive power optimization model based on regulation cost is established. The model aims at the operating cost of reactive power compensation, the minimum cost of transformer tap action and the minimum loss of active power network and node voltage deviation, and obtains the optimal action of reactive power compensation and transformer tap. The example considers the actual situation of the auxiliary system such as the access location of renewable energy power supply and reactive power compensation device and the characteristics of daily load curve, and verifies the validation of the supplied model and algorithm by simulation.