In order to solve the problems of transporting, such as complexity of the mechanism, high cost of the electrical control system, pot damage in the process of transplanting, a new automatic seedling transplanting device was designed, which consists of vertical movement mechanism, ejecting mechanism, horizontal movement mechanism, guiding mechanism and gripping mechanism. The specific form of each mechanism were determined by using F-P-A method. The cam’s maximum pressure angle was determined as 29.32° and the cam displacement was determined as 29mm according to agricultural requirements using virtual modeling, simulation and accuracy analysis. The sequence analysis model program was built with the Visual Studio software, and a group of optimal parameters was obtained with this program. The initial phase angle of vertical mechanism was 185°, initial phase angle of ejecting mechanism was 108°, the length of the crank was 78mm, the length of the connecting bar was 112mm, the eccentricity was 20mm, the initial phase angle of the gripping mechanism was 15° and the initial phase angle of the opening and closing mechanism was 135°. The experiment was done with three different moisture contents of the tomato seedlings aged 45 d. The experiment result showed that the moisture content and gripping speed both had impacts on the success rate of the seedlings, and both had negative correlation, the gripping speed had little impact on the damage of the seedling. This device had the performance that the maximum gripping speed was 140 plants per minute at which the success rate of gripping was above 95%, and the success rate of gripping was 98.44% and the damage rate of the seedling was 36.67% at the condition that the moisture content was 32.79%, which meets the agricultural requirements and was faster than the manual.