In this research, amount of effect of Mediterranean Sea surface temperature anomalies on precipitation of West of Iran has been investigated. For this purpose, warm, cold and base periods were determined for dates of MEDSST in statistics period of (1970–2005) for every season. Then Medians of precipitation in every season and every period were determined so as Rw, RC and Rb. Theses Medians in every season and every period compared together to clear amount of this effect. Results indicated when MEDSST is colder than normal in winter season, winter precipitation of West region of Iran increase but MEDSST of warmer than normal in autumn season is caused increase of precipitation. There is negative and confident correlation between MEDSST anomalies and precipitation of some station of West of Iran in winter season and also there is positive and confident correlation between MEDSST anomalies and precipitation of many station of West of Iran in autumn season.