Abstract: The anti-jamming performance of adaptive array is commonly measured by signal-to-interference and noise ratio (SINR) loss and electronic counter countermeasures(ECCM) improvement factor (EIF), which lack quantitative analysis via analytic expressions. Therefore, the analytic expressions of the two performance indexes are theoretically derived using the inductive method, based on the uniform linear array (ULA). Finally, the simulation results are also provided to demonstrate the effectiveness of the proposed method and the anti-jamming performance is also analyzed under the condition of the finite sampling snapshots.