The present invention relates to the field of cultivated land identification, in particular to a method and device for identifying effective cultivated land. The method and device use long-time sequence Landsat TM remote sensing data as a data source, use slope SLOPE data as auxiliary data, and use normalized differential vegetation The index NDVI is used as a classification feature, based on the phenological differences of crops on agricultural land, and reflects the differences in planting period, spectral difference and other characteristics of crop species to the distribution of time-series NDVI data, and designs a normalized difference The object-oriented decision-making classification rules combined with vegetation index NDVI and other classification features can not only extract the spatial distribution information of some crops on agricultural land, especially in West Asia, but also understand their cultivation conditions without considering the complex vegetation of different crops. However, the data source required by this method is easier to obtain, the amount of data to be processed is small, the classification rules are simple, and the work efficiency is high. It is also applicable to areas where the distribution of cultivated land is relatively fragmented.