Given the limitation of optimization models of grid-connected wind capacity in dealing with randomness of wind power， a novel optimizing flexibility model based on the research on flexible analysis of power system is proposed， considering the influence of operation value of wind power. In this model， the randomness of wind power is expressed by introducing flexible parameters and quantified as a penalty cost into the operation value of wind power. By adopting the saddle node theory of Lagrange function， the multi-objective optimization problem is transformed into two single-objective problems. The calculating results on IEEE 30-bus system demonstrate that the model reflects the randomness of wind power adequately， and the economic and security of planning are combined organically by adopting the proposed model. It enables a compromised decision-making between grid-connected wind capacity and operation value of wind power.