Abstract: At present, the research on the mechanism of vegetated slope mostly focuses on the mechanical effects rather than the hydrological effects of vegetation roots, and even there are some studies focusing on the hydrological effects, and most of them only focus on the water uptake and transpiration of single plant roots. In order to investigate the effect of plant spacing on hydraulic characteristics of the vegetated soil, such as the soil suction and water content at different depths, in multiple plants conditions and the drying-wetting processes, monitoring on the soil suction and water content at the observation points were carried out in the model tests composed of the vertical geotextile belts (water-retaining and reinforcement belts) and vegetation, in which the plant spacing was 20, 30 and 40 cm respectively. The model test results show that the maximum suction of the soil in the test with a plant spacing of 20 cm was 5.3% and 43.3% higher than that of the test group with a plant spacing of 30 cm and 40 cm respectively during the drying process. It can be concluded from the model test results that the smaller the plant spacing is, the more intense the water competition between plants, and the more obvious increase of suction in the soil. Within the root depth of vegetation, the suction and volumetric water content of the soil decrease with the depth of the soil, and the soil below the root depth is basically unaffected. Under the rainfall condition, rainwater preferentially infiltrates into the soil along the cracks, so the slope should be prevented from cracking. Since the vertical geotextile belts are installed on one or both sides of the plant root system, the plant spacing is actually the distance between the vertical geotextile belts. When the geotextile belts are used for slope protection, the distance between geotextile belts should not be too large, and they should be arranged under the principle of “fine and dense” in accordance with the cost and the spacing of plants.