Soil-water characteristic curve is usually used to estimate the shear strength of unsaturated soil. In consideration of the water absorption and reinforcement effect of plant roots

the shear strength of plant slope can not be directly calculated by the formula of unsaturated soil shear strength based on matrix suction.In this paper

the bare slope and vegetation slope are taken as the research objects

and the soil and water characteristic curve of the test soil is obtained by combining the tensiometer field test and indoor shear test. The results show that the plant root implantation can effectively improve the air intake value of slope soil

which is 41.10% higher than that of plain soil. Under the same water content

the matric suction of plant slope is significantly higher than that of plain soil slope

which improves the water holding capacity of slope soil.The Van Genuchten model can be used perfectly to fit the datum from the soil water characteristic curve. With the increase of water content

the shear strength parameters of the soil with root and plain soil are similar

which are both increasing first and then decreasing. But the change parameters of the soil with root are large. When the water content is 21.29%

the cohesion of the soil with root increases by 4.86 kPa

and the increase is 18.55%

while the sensitivity of the internal friction angle to the root system is not as good as the cohesion.With the increase of soil matric suction

the change trend of mechanical parameters of shear strength of vegetation slope and plain soil slope is basically the same

and the cohesion of soil increases most obviously in the range of matric suction of 60~90 kPa. However

the matric suction of vegetation slope increases the shear strength of slope soil more greatly due to the existence of plant roots

The maximum increases of cohesion and internal friction angle are 37.34% and 40.30% respectively.By establishing the relationship between the parameters of soil water characteristic curve and the shear strength of plant slope

the shear strength of plant slope under different water content or matric suction can be calculated

which provides a theoretical basis for further analysis of the stability of plant slope in engineering practice.