Abstract: Based on one-way diffusion, double membrane theory and effective membrane model, the external moisture transfer models of Dutch cucumber in the beginning of storage was built, which was called analogous diffusion in one-way direction. Then the effective film thickness was derived through experiment on water evaporation strength of Dutch cucumber under the condition of constant temperature and humidity, which avoided problem that it was difficult to determine thickness of effective film during analyzing its moisture transfer process, and provided a new thought for forecasting the water loss of fruits and vegetables in the beginning of storage.