To address the problem of insufficient system reserve capacity caused by high wind farm penetration, a multi-objective optimal allocation method for energy storage reserve capacity considering line flexibility carrying capacity is proposed. First, the concept of line flexibility carrying capacity is introduced, and a multi-objective optimal model for energy storage reserve capacity allocation is constructed. Second, for solving the constructed multi-objective optimization model, an improved normalized normal constraint is proposed, which avoids the inclusion of locally dominated solutions in the Pareto solution set. Finally, case studies on the modified IEEE39-bus system show that the proposed method can not only effectively alleviate the reserve shortage problem caused by high wind power penetration, but also reserve sufficient transmission margin.