This paper has studied the seed coat effect during the process of unsteady drying for vegetable seed, using biological optical microscope to make an exploratory research on the variation of the seed coat structure, combining the seed coat biological function to probe into the mechanism of optimizing heat and mass transfer for seed drying. This paper has studied the seed coat effect during the process of unsteady drying for vegetable seed, using biological optical microscope to make an exploratory research on the variation of the seed coat structure, combining the seed coat biological function to probe into the mechanism of optimizing heat and mass transfer for seed drying.