Abstract: Farmland shelterbelt is an important component in the Three-North Shelter/Protective Forest Program. To accurately estimate the quantity and spatial distribution of the farmland shelterbelts in the Three-North regions (west of Northeast China, north of North China, and most part of Northwest China) is of significance to understand the protective effect of these shelterbelts and to promote their construction processes. Based on the multi-scale remote sensing data to acquire shelterbelt length and the field survey data to obtain shelterbelt width, this paper estimated the farmland shelterbelt area in the Three-North regions that were topographically divided into four areas, i.e., Northeast China, North China, Loess Plateau, and Northwest China. The shelterbelt length in Northeast China and North China was acquired from the relationships between the shelterbelt lengths from SPOT5 and Landsat TM, while that in Loess Plateau and Northwest China was obtained from the relationships between the shelterbelt lengths from CBERS02B and the farmland areas from Landsat TM. The results indicated that in 2008, the total length of the farmland shelterbelts (including middle-aged, mature, and over-mature shelterbelts, and excluding new planted, un-matured, and part of declined shelterbelts) in the ThreeNorth regions was 106.40×10⁷ m, including 23.82×10⁷ m in Northeast China, 6.07×10⁷ m in North China, 25.58×10⁷ m in Loess Plateau, and 50.93×10⁷ m in Northwest China,

 and the total area of the farmland shelterbelts was about 130.31×104 hm2 (114.98×104-145.64×104 hm2), including 42.38×104 hm2 (37.52×104-48.24×104 hm2) in Northeast China, 10.92×104 hm2 (9.56×104-12.29×104 hm2) in North China, 25.58×104 hm2 (22.70×104-28.45×104 hm2) in Loess Plateau, and 50.93×104 hm2 (45.20×104-56.66×104 hm2) in Northwest China. The mean accuracy of the estimation was 89.54% (79.27% in Northeast and North China, and 99.80% in Loess Plateau and Northwest China).