In Iran the issue of occurring natural disasters, particularly mesoscale convective systems. They are important on one hand, because of their increasing intimidations and causing damages and on the other hand, because of their increasing abundance, time of duration, and happening. Therefore life cycle, constituton condition and mesoscale convective systems features in west of Iran using satellite and extention area index and thresholds of brightness temperature 221 and 243 K have been studied. After their statistic analysis, based on mesoscale convective system importance, life and daily cycle, behavior parameters, and synoptic conditions of this system life cycle were analysed. Most of the systems have been formed in southeastern Iraq and in western Zagros hillsides. Wile puberty stages (the maturity) and their expandings were increased with the height increase; in turn, declining of the systems began by passing Zagros chain mountains. The system extention area at the system life cycle starting increases with a smooth process; whereas the reduction process of the system extention area at the declining stage was severe and sudden.