Abstract: According to the structural characteristic of the tomatoes and taking two-dimension problem as the research target, the mechanical model of tomatoes was established. The method using linear fitting to experimentation data for mechanical parameter of the object was gained. The relationships of the external pressure, compressing distortion and stress of tomato epidermis when tomatoes were compressed were investigated. The theoretics directions for all kinds of concerned design and manufacture of mechanism, prognostication of mechanical damage, improvement of production quality were offered. The relationships between compressing distortion and external pressure, inner-pressure and stress of tomato epidermis are not linear, while the relationships between inner-pressure and the external pressure, inner-pressure and epidermis stress of tomatoes, epidermis stress of tomatoes and the external pressure are linear approximately. Moreover, the change of tomatoes area increases linearly when the external pressure increases, and the tomato epidermis that is not subjected to force ruptures firstly.