本文研究（Ⅰ）和（Ⅱ）类系统Dulac函数的构造问题，作为应用，讨论此两类系统的极限环的不存在性问题，得到了一些新结果．

In this paper, we study structure problems of Dulac function for quadraticsystems of Type (Ⅰ) and Type (Ⅱ). As its application, we discuss the question of thenon-existence of limit cycles and obtain some new results.