According to the impact of the wind power prediction uncertainty on the power system reserve capacity, the reserve capacity model based on the uncertainty of wind power is established. First, the method of scenario is used to simulate the uncertainty model of the wind power, load and conventional generators, then the probability statistics on these scenarios is given in order to obtain the probability density of the system power difference, and the expected energy not supplied (EENS) and expected wind waste risk (EWWR) are presented; the reserve capacity is determined by the two aspects which are the reliability of EENS and EWWR and the economy of reserve capacity cost. Finally, simulations on a ten-unit system are given to demonstrate the method is effective to reduce the cost of reserve and the abandoned wind power in the context of system reliability.