Runoff and sediment measurement is difficult in mountain watershed because of many different problems such as time and financial limitations. So using simulation model is necessary in this regard. Accuracy and precision evaluation of models for different watershed of Iran is necessary. The aim of this study was the evaluation of SWAT model efficiency in simulation of runoff and sediment yield in Chelchay watershed in Golestan province, Iran and also calibration and validation of SWAT. SUFI2 algorithm was used for calibration and validation. Nash-Sutcliff for calibration period (2001-2005) and validation period (2006-2009) for average daily discharge was 0.5 and 0.4 respectively and for sediment concentration was 0.71 and 0.92 that is good according to past research results. Because SWAT is complex and integrated model and can be used as a management tool in watershed management so it is suggested that it would be used for evaluation of management activities effects in Chelchay watershed.