These results shows quantitatively the decrease in physiological activity of samples inhibit shrinkage of sample surface area during hot air drying. So, this study clearly demonstrate that a decrease in the physiological response of spinach with heat pretreatment was one of the factors resulting in the increased hot drying rate of spinach samples because the shrinkage of sample surface area was inhibited. We also propose that the Fv/Fm might be a suitable index to evaluate the life activity of spinach during the hot air drying process. New drying techniques for increasing the drying rate could be developed by optimizing the heat pretreatment of spinach sample, and the technique will be useful for constructing cost effective dried spinach production process.