介绍了经典中距拦射空空导弹无线电修正指令的形成原理及存在的问题，并分析了原因。提出了变周期中制导指令的方式，并建立了基于目标当前统计模型的变周期指令模型，将目标运动状态预估计值融入中制导指令，以中制导剩余时间估计为根据,改变中制导指令周期。仿真结果表明，改进的指令模型提高了导引头偏离角跟踪的效能并限制了截获时的目标指示角误差。

The principle and the existing problems of radio amendment instruction consisted in the classical mediumrange airtoair intercept missile are described. Then a new method of variable period midguidance instruction is proposed. A variable period instruction model is established based on the Current Statistical Model (CSM) of target. The predicted target motion value is introduced into midguidance instruction,and the period of midguidance instruction is changed according to the estimated remaining time of midguidance. The simulation result indicates that the modified instruction model can improve the tracking efficiency of seeker and limit the error of targets designation angle in intercepting and capturing.