Abstract: Microaggregate is a basic structural unit in natural cohesive soil, composition of microaggregate and its stability and strength in the presence of water are the important factors determining the engineering property of the cohesive soil. A comparision between results of granulometric and microaggregate compositions of two study of causes for formation of water stable and water unstable microaggregates. From the obtained data we discuss the engineering properties of the soils in the paper.