Abstarct: In longwall mining method, the stability of the maingate and tailgates are of high importance because these tunnels are used for the services such as ventilation and transportation.considering the points mentioned, any failure may cause major fatalities and loss in production of mine.the purpose of this study is to investigate the stability of the maingate tunnel between two panels and its effect on the support systems and the stress states within simultaneous exploitation and caving on numerical approach using FLAC3D software. In this study, in order to determine the caving of the stope and the stability of the P8-Maingate tunnel sakurai critical strain is used. The results of numerical modeling showed that the first caving occurs in 10 meters and the periodic caving occurs during the caving cycle on the advance of stope cribs behind the stope. According to the sakurai criteria, the P8-Maingate tunnel is stable.