Abstract: This study is conducted in the second forest of Chi-Lan village and Yu-Lan tea garden of Ta-Tung country in Yi-Lan. We measured the latent evapotraspiration by evaporation disc method at the two study sites and tried to understand the difference of the evapotranspiration on the different land use type. We hope the results of this study can afford the reference for the concerned authorities and the land developer. The study results show that the latent evapotranspiration over the garden ecosystem is clearly higher than that in the second forest ecosystem. We think the reason is that the garden ecosystem is an open system and the whole open system is exposed to the sunshine so it can accept sufficient solar radiance and resultsd in the higher latent evapotranspiration. While the situation in the second forest ecosystem is quite different because the plants in it have different heights and cover each other,which results in receiving less solar radiance. Furthermore,there are many deep-root plants in the second forest ecosystem so the characteristics of soil and water conservation are relative better than the garden systems. The results also suggest that the loss of the water content in per hectare land will increase 100～150 tons when the second forest ecosystem is developed as the garden ecosystem in winter.