Heavy rainfall is one of the most important climatic events, and if the correct planning is not done, it will have destructive environmental and economic impacts and will be removed without exploitation. This study is trying to forecast changes of the future heavy rainfall  in southern coasts of the Caspian Sea with regard to global climate change in the period of 2011-2030. For this purpose, changes in the pattern of 10, 20 and 25 mm and more rainfall were analyzed based on rainfall data of six synoptic stations (Anzali, Astara, Babolsar, Gorgan, Noshahr, Ramsar and Rasht). Daily rainfall data was simulated in the period 1961-2009, after verification of their accuracy and Correctness, using the Lars-wg model. After comparing the simulated values with the current period data, the daily rainfall values were predicted for the upcoming period (2011-2030). The eleven indexes of the R-Climdex global model were calculated for the current period and the upcoming period. Among these, three heavy rainfall indicators (R10mm, R20mm, R25mm) were analyzed. The results show that at most stations in the area in the upcoming period, the total number of days with rainfall of 10, 20 and 25mm will be added (other than Nowshahr station and Ramsar station). Overall, among all the stations studied, Anzali station will experience the largest number of days with heavy rainfall of 10 mm and heavy rainfall of 20 and 25 millimeters.