Mapping and analyzing the agricultural lands using remote sensing and GIS technique is faster and cost-effective compared to conventional site verification method. Thanjavur is a district in Tamil Nadu which rich in agriculture. It is a lower riparian of Cauvery river. It is rich in alluvial soil, but its crop production is falling due to urbanization and water insufficiency. Failure of monsoon and insufficient river water are also major reasons. Since agricultural lands are depleting, the cost of agricultural products is increasing. LANDSAT 7 imagery is processed using ARC MAP 10.4 and classified using ERDAS IMAGINE 2014. By analyzing the results obtained through the process for decade 2009-2018 we concluded the percentage in area change for agricultural lands with crops and without crops, barren lands, urban areas, and water bodies. The study is to determine the drop in agricultural lands and its causes.