A set of ecological benefit evolution index was established by method of Analytic Hierarchy Process (AHP) based on observation data in the farmland shelterbelts of Minqin oasis. It was found that the ecological benefit of farmland shelterbelts was predominantly determined by wind-defending benefit. Besides, change of temperature and humidity in shelterbelts, and variation of soil organic matter and soil moisture were also the important influencing factors.The wind-defending benefit has close relation with hierarchical structure and porosity of farmland shelterbelts. Results of integrated evaluation indicated that shelterbelts that have proper porosity and whole forest structure can well protect the farmlands in comparison with that have ventilation or tight structure and incomplete forest structure.