In this article, the relationship between the falling height and the planting depth of seedlings and the static and kinetic friction coefficients between the potted-seedling bowls and different materials of canal were researched, which provides the theories for designing the rice potted seedling transplanter. The experimental results show that the planting depth of seedlings increases when the falling height of seedlings increases. In the common soil and the field in normal quality, the planting depth of seedlings is between 4.8 mm and 12.5 mm when the falling height of seedlings is between 0.75 m and 1.5 m, the depth meets agricultural requirement. The friction coefficient between the potted-seedling bowl and the steel plate is almost the same as that between the potted-seedling bowl and plastic plate. The planting depth is affected by the relative humidity of the potted-seedling bowl. The planting depth increases when the relative humidity increases and it is the most when the relative humidity is about 80 percent. When designing machines, it is adopted that the max friction angle is 35° and the friction coefficient is 0.7.