The aim of this study is to investigate synoptic change's monsoon system, South East Iran. Since precipitation is indicative instability and influx moisture, Precipitation's sweeping of the area was considered as a base to expand monsoon into Iran. The data include precipitation in synoptic, rain-gauge stations and NCEP-NCAR data. Grad's software was used for mapping. The results showed that in surface, the establishment of a broad low pressure in the Persian Gulf, Pakistan and expansion tab of Turkey high-pressure for a trough along the Zagros is responsible for the spread of monsoon. In 500 ha in events 1, 2 and 4, create a trough and positioned in the eastern areas in front its and in the third event the sawed-off tabs Russia for Cutoff low on Afghanistan, caused monsoon system penetration into the Iran. The profile of the area Omega is representing negative Omega at this time. Following lines showed the establishment the cyclone over the Indian Ocean in events 1, 2 and 4 and on Afghanistan in event 3 the groundwork for expanding the monsoon system. Events 1, 2 and 4 field of shared water systems that come from India, while the event 3 moisture is provided from Afghanistan that actually the tab moisture that has penetrated through India to Central Asia. Furthermore, monsoon expanded with positive vorticity is at ground level and negative vorticity at 500 hPa level.