In order to understand the windbreak and sand fixation effects of the Three-North Shelter Forest Program (TNSFP) in recent 35 years, this paper analyzes the amount change of ecosystem sand fixation caused by climate change and vegetation degradation or restoration in the project region, and then assesses the sand fixation effects of the Program. Based on Landsat MSS, TM/ETM+, and environmental satellite (HJ) images, the spatial-temporal datasets of land cover changes in the project region of TNSFP were analyzed in the periods of mid 1970s, 1990, 2000, 2010, 2015, especially the forest and grassland. Combining the NDVI data of AVHRR and MODIS, the vegetation coverage was estimated, and then the change of vegetation coverage in the 1982-2015 was analyzed. The soil erosion modulus were estimated at the regional scale by applying the soil erosion equation (RWEQ), and then the ecosystem services of windbreak and sand fixation were assessed using indicators of amount and retention rate of windbreak and sand fixation. Then the contribution rate of ecological program and climate change to regional ecosystem change was determined by comparing the indexes under the conditions of average climate and real climate. The results showed that: 1) In the past 35 years, the area of forest was continuously increased and grassland was decreased, especially in the semi-arid sandy area and Loess Plateau. The vegetation coverage increased continuously in the before 20 years, and then decreased in recent 15 years. 2) The soil wind erosion modulus is decreased continuously, and the decreasing rate in recent 15 years is much higher than that in the before 20 years. The decreasing rates were especially obvious in sandy land, grassland, and regions planting trees and grassland. The retention ratio of ecosystem windbreak and sand fixation service also increased continuously, especially in arid desert area. Grassland and sandy land contributed 71% of the total amount of windbreak and sand fixation. However, just 6.6% of forest land, and the contribution of conversion grassland was higher than that of conversion forest. 3) In the TNSFP, the weakening of wind erosion force due to reducing wind, and the vegetation restoration in local areas due to TNSFP and other ecological programs, both resulted in a decrease of soil wind erosion, and accounted for 85%-89% and 11%-15% of the decrease. Winter monsoon in mid-latitude Asian is weakened due to global warming. In the project region of TNSFP, the grassland played the most important role in ecosystem service of windbreak and sand fixation, which accounts for more than 63% of the total area. Therefore, the conservation of grassland and sandy land were significant in project region of TNSFP. Project planning and implementation should focus on the transfer of funds from afforestation to grassland conservation and restoration.