The active power pricing model of power system based on the security region is applied to the feasibility study of wind farm location and its capacity. The hourly averaged daily generation curve is used to express the wind farm operation constraints， and the load changes over time are reflected through the scaling factors. Due to the consideration of line thermal stability constraints and transient stability constraints in the model， the impact analysis of location and capacity of wind farm on the market price and generation cost as well as security cost is more in line with the actual results. The studies on New Zealand 10-machine-39-bus system show that the method can help power system planners assess the integration of wind farm more scientifically.