A wind-power balance cost allocation method was developed in response to China’s goal of increasing wind-power consumption capacity and achieving sustainable development, combined with the need for electricity spot market construction. The proposed method considers the spatiotemporal characteristics of wind power and the impact of relative load power fluctuations on system operation. The “equal electricity quantity following load” method was used to construct a zero-wind power balance cost equivalent scenario to optimize and dispatch system operation in advance. By comparing the predicted scenario with the equivalent scenario of the optimized dispatch, the total operating cost of wind power balance was solved for the dispatch cycle. Based on the spatial distribution and capacity of each wind power plant, a balance cost allocation model between wind power plants was established. An indicator, the relative fluctuation rate of each time period, was proposed to quantitatively express the temporal evolution characteristics of wind-power relative load fluctuations, and the corresponding model was established. Based on the relative fluctuation rate of each time period, the local fluctuation impact factor was obtained to allocate the wind-power balance cost of the dispatch cycle by time period, resulting in wind power balance costs for each time period. Using the grid structure of a region with a high proportion of wind power as an example, the balance costs of different wind-power grid capacities and fluctuation levels were calculated to verify the effectiveness of the proposed calculation method and model.