Among the methods of jamming the direction-finding system of the guide head of a missile, twinkle jamming is generally considered a kind of rather available method. To a great extent, the effect of twinkle jamming lies in the distance between the emission sources and the twinkle frequency. This paper presents a new rule to evaluate the jamming effectiveness - least variance - to - expectation ratio rule. And based on this rule optimization algorithm of twinkle jamming by two planes is elucidated.