[Objective] The effects of the geometric characteristics of the shrub root on pulling force is studied in order to provides a theoretical reference for the selection of plant species and the full utilization of plant value.[Methods] Taking photinia fraseri as an example, the outdoor pull-out test of photinia fraseri root system was carried out to study the interaction between root and soil in different water gradients, root form, secondary side root and so on.[Results] The maximum pulling force of the Y-type root system and horizontal root system decreased logarithmically and exponentially with increasing moisture content. However, the maximum pulling force of the main direct root system increased first and then decreased with the increase of water content,and the optimum moisture content was about 17.5%. The maximum pulling force of the Y-type root system increased with the increase of the root system angle. The activation time of the root system increased first and then increased with the increase of the angle of the root system. It was most easily activated when the angle was 75°. The maximum tensile force of the Y-type root system and the main direct root system increased linearly with the increase of the number of secondary lateral roots, but the increase of the maximum tensile force of the main direct root system was greater than that of the Y-type root system. The drawing curve was drawn hardened when the water content was 10%, 20% and 25%,and the drawing curve was a pull-softening type when the water content was 15%. When the horizontal root system and the Y-type root system were in the water-bearing rate of 15% and 17.5%, the drawing curve was drawn hardened, and when the water content was 20%,22.5% and 25%, the drawing curve was a pull-softening type. Through the comparison of the effects of different root system slopes, the mechanical of the multi-form root vegetation slope was evaluated, which had a theoretical guiding effect on ecological protection.[Conclusion] Root morphology and water content are the key factors affecting the pullout force of roots. The more complex the root morphology, the greater the pulling force. As the water content increases, the drawing curve gradually changes from hardening to softening.