本文得到：具有细链双曲无穷远鞍点和一个细焦点的二次系统至多存在一个极限环，若有细无穷远分界线环S，则其内部不存在极限环，其稳定性与它包围的奇点的稳定性相反．

In this paper, we prove that a quadratic system with a weak focus and weak pairing infinitehyperbolic saddles has at most one limit cycle, and that if this system has a weak infinite homoclinic loop, then its stability is contrary to that of the singular point surrounded by it, and this system has no limit cycle in the region formed by it.