Semnan province is one of the vast provinces of the country that has a variety of topographical and clamatorial conditions. This province plays a key role in industrial, agricultural and animal husbandry activities. The study of its climate potential with respect to its natural limitations like lack of water resources, soil types, droughts and desertification problems has been considered as a necessity in the province annual planning. In this study, the climatic regionalization of the province is done through using empirical and quantitative methods on climatic data of meteorological stations of the area in statistical period of 1982-2005. Methods of Koppen empirical, De Martonne, Emberger and Dr Karimi have divided the province into 3, 2, 4 and 6 climactic types, respectively. Using principle components and the cluster analysis on 14 climatic elements of 21 stations, 5 climatic types have been specified for the province. Based on this method, temperature, its Diurnal Temperature Range (DTR), precipitation and its type, and humidity contribute a great deal to the climate of the Semnan Province. The main results of this identification of 5 climatic types include hot & dry, dry & hot semi-dry, dry & cold semi-dry, mountainous, and Caspian climate.