Abstract: It is proved that shear strength of unsaturated soil is related to matric suction. However matric suction has close relationship with water content. Based on the results of the laboratory test and theoretic analysis, the effect of water content on unsaturated soil shear strength indices c and φ is investigated. At the same time, the effect of matric suction on unsaturated soil shear strength indices c and φ is discussed by the soil-water characteristic curve(SWCC). Based on the tests,the value of c decreases as the value of water content w increases and the value of matfic suctionμ decreases. The value of φ has little change By linear regression analysis, the conclusions is indicated that cohesion has semilog linear relationship with water content and cohesion is directly proportional to matric suction. The precisions of the previous aren't satisfied and further research is needed. With the development of unsaturated soil mechanics, researches on unsaturated soil shear strength indices should be strengthened.