In order to improve the complicated seedling picking and throwing mechanisms of domestic vegetable transplanter, an airblowing combined with vibration type seedlings unloading mechanism was designed based on a modified seedling tray at first. And the designed mechanism was composed of three main parts which were feeding device, vibrating device and airblowing device and each part was cooperated to complete the automatic picking up and delivering seedings work. After that, the dynamic models of seedling and seedling tray were established during the seedlings unloading process. Through analyzing the models, the frequency of vibration, the amplitude of vibration and the water content rate of substrate were three main influence parameters which had effects on success rate of seedlings unloading. Furthermore, a multiobjective orthogonal test was performed considering the vibrating device and airblowing device comprehensively. The success rate of seedlings unloading and the damage rate of substrate were chosen as the evaluation indexes, meanwhile the water content rate of substrate, the frequency of vibration and the air pressure were selected as the experimental factors. And the results indicated that when the water content rate was 55%, the vibration frequency was 36Hz and the air pressure was 0.45MPa, which were the best combination factors, led to a satisfactory result with 92% of success rate and 3.46% of damage rate. The result was able to provide a reference for automated transplanter.