During the up-film transplanting for dibble-type transplanters, the mulch film could be easily dilaceraded and scraped. Aiming at this problem, a pot seedling transplanter in duck-beak style was designed while the working principle of it was expounded. The motion mathematical model of its planting mechanism was established. And then, parametric modeling for the planting mechanism based on the model was completed in ADAMS. The influences over the mechanism motion characteristic by some important parameters were analyzed by using the parametric model. In addition, the cave value which formed by the distance between two intersections points of the duck-beak trajectory and ridge line as possible as small was taken as the optimization objective, while the higher upright degree of seedling was ensured. Meanwhile, the optimal parameter combination of planting mechanism was obtained. With it, the cave value was 1.8mm and the verticality of duck-beak trajectory after transplanting seedlings was higher, and then the demands of up-film transplanting could be met, namely higher upright degree of seedling and without dilacerating films.