The invention provides a method for determining reactive compensation of a photovoltaic access station. The method comprises the following steps: setting reactive compensation capacity of the photovoltaic access station; carrying out overall process analogue simulation according to the initial reactive compensation capacity and simulating whether voltage fluctuation under an impact condition of photovoltaic power fluctuation meets the operating requirements or not; and adjusting the reactive compensation capacity according to the simulation result. Furthermore, the invention further provides a device for determining reactive compensation of the photovoltaic access station. By the method and the device, the operation risk of a large-scale photovoltaic access system is reduced; the ability of a power grid for resisting a voltage instability risk is improved; and the safe, stable, efficient and economic operation level of the power grid is improved.