The Zagros mountain forests in Iran, constitutes approximately 40 percent of the country’s forests expanding in eleven provinces, provides important functions as soil and water preservation. The forestes sustained severe oak decline in places over the last decade, triggered by chain factors such as drought, pathogens and Borer beetles. Determining the extent of the declined regions is the first step to address manage and address the risk posed by such environmental hazards. In this research, we focus on Malekshahi city in Ilam province and use Landsat satellite images in years between 2000 and 2015 for determining spatial pattern of oak decline in this region. Slope of temporal variation of an appropriate vegetation index and a water index, are extracted and analyzed from Landsat imageries. The oak forests are classified in three categories: Healthy forests, low-severity declined forests, and high-severity declined forests, based on EVI and NDWI. According to the results, approximately 16%, 58% and 26% of the region belongs to healthy regions, low and high level of disease, respectively. Finally, the overall accuracy of the oak decline map, is evaluated based on available ground truth data. About %83 overall accuracy, shows high performance of the proposed method in detecting declined regions against healthy ones. But it has less ability in classifying different levels of decline, since overall acccuracy is about %54 for this purpose.