The purpose of study is to investigate the large environmental factors associated with the occurrence of tropical cyclones(TCs)in the Arabian Sea and the Gulf of Oman in the recent10 years period.Therefore,the meridional and zonal winds,relative humidity,sea surface temperature,sea level pressure,air temperature and specific humidity were extracted from ECMWF reanalysis database.Then were calculated the values of dynamic factors absolute vorticity,vertical wind shear and thermodynamic factors including relative humidity and potential intensity.Also,tropical cyclones’data were extracted from theJTWC.at the first step,the monthly mean of absolute vorticity,vertical wind shear,potential intensity and relative humidity were calculated in a 10 years period by using GRADS and MATLAB during monsoon, pre and post-monsoon, and the required maps were plotted. Then,some of the most powerful cyclones occurred in these months were selected and dynamic and thermodynamic components of them were analyzed.The results showed that the northern parts of the Arabian Sea,at 15-22°N and 62-75 °E in June had a favorable environmental condition for the occurrence of TCs.Considering the availability of large scale environmental parameters values in the Gulf of Oman in June,these events are a serious threat to the coast of southeastern Iran.The formation potential area expands to southern latitudes in May,October,November and December. In September,there are some favorable conditions for cyclone formation in the north of the Arabian Sea, but potential intensity and the relative humidity are very low.The calculation of the average daily quantities in the duration of activity of the strongest storms also approves the effect of environmental elements on the formation of tropical cyclones.