本文证明了具有二个焦点的二次系统必在其中一个焦点外围至多有一个极限环这一猜想．从而得到具有二个焦点的二次系统之极限环必是（Ｏ，ｉ）或（１，ｉ）分布（ｉ＝ ０， １， ２，）．

In this paper it is prove that a quadratic system with two foci has at most one limit cycle around one of the two foci, and hence the limit cycles of the quadratic system with two fool must be (0, i)-distribution or (1, i)-distribution (i = 0, 1, 2,...).