In order to improve the upright degree and reduce the damage in the process of transplanting for the film transplanting machine, a crankchute planting mechanism was designed and the mathematical model of this mechanism was built. The optimization program of mechanism was programmed on the base of the model with the Matlab software, and the influence law of the key parameters of this mechanism on the trajectory of the planting point was analyzed. The upright degree was chosen as the optimization indicator, which is, the insert point and the leaving point is perpendicular to the soil ridge as much as possible and these two points should be close to the planting point as much as possible. With the optimization program, a group of optimal parameters of this mechanism were obtained, that means, the velocity of the machine, which was 500mm/s, the length of different bars including L1=150mm, L3=120mm, L4=310mm, L=680mm, different angles including θ1=10°,θ3=15°, θ=20°, and with these parameters the trajectory of the planting point was γ，which was beneficial to the seedling to be upright and had less damage to the film. The experimental prototype was manufactured according to the optimal parameter, the field experiment was done with the tobacco seedlings chosen as the experiment object, the experiment result showed that the upright degree was above 93%，and the damage rate of the planting mechanism on the film can be diminished to 8%.