Abstract: In order to improve the germination rate via mechanical seedcoat nicking method instead of manual operation. The germination hindrance of triploid watermelon seed was analyzed by seedcoat ultrastructure features compared with diploid watermelon seed. Familiar watermelon seeds of three varieties, Heiniu, Mihong and Huapi, at the moisture content of 11.1, 11.2 and 10.6% (w.b.), were selected to study the mechanical nicking properties using common methods, respectively. Test results showed that the loading speed of pressure had an influence on the seedcoat nicking force. The maximum compression values of all seeds were as the designing standard for the compressing rocker. The loading speed of pressure was chosen as 80-100 mm/min; the maximum nicking force as 68.97 N. It is concluded that the results provide basic parameters and theoretical basis to design a seedcoat nicking machine for triploid watermelon seeds.