本文称圆锥曲线焦点所在的对称轴为主轴 ,并阐明主轴上点的一种配对关系 .设圆锥曲线Γ的离心率为 e,一个焦点为 F,主轴为 l,在 l上距 F较近的顶点为 O.定理　设 M、N为 l上满足关系　　 1OM+ 1ON=1 - eOF (* )的两点 ,则对Γ的过点 M的任一弦 AB(A、B为弦的端点 ) ,l平分直线 This article describes the symmetry axis where the conic curve focus is the main axis, and clarifies a pairing relation of the points on the main axis. Let the eccentricity of the conic curve Γ be e, a focus point is F, and the principal axis is l, which is closer to F on l. The vertex is O. Theorem Let M, N be the two points on the l satisfying the relationship 1OM + 1ON = 1 - eOF (*), then the point AB of the point M of the enthalpy (A, B is the end of the string), l Straight line