Abstarct: The study area is the part of Minab city located in the east of Hormozgan province and between structural zones Zagros and Makran. The major deformation in area is accommodated by folding and faulting. The structures of the area anticlines and synclines which are parallel general trends are approximately north-south to northwest - southeast. Major of variation are observed in vicinity of minab fault. The growth of folds is affected by reverse fault related with minab fault. In this investigation first which has been, studied in minab dam and surrounding in two stages. First neo tectonic activities in the region is investigated, and then to estimate the permeability and water leakage from the rock mass of the reservoir minab dam focused on office and field is studied too. Minab fault is studied for Evaluation of tectonic and neo tectonic activities, the minab fault in the northern part of it, has affected and cut quaternary deposits. In the first case in the east of Minab-Bandar Abass road, and near the village Domshahr where the Minab fault is the boundary of alluvium and the mountains some findings on the quaternary deposits of the fault has been observed in trenches drilled for construction projects, and also the shear affects of the fault on a river terrace in the northeast of the village Domshahr, indicate quaternary fault activity. Another activity of this faut, tertiary quaternary deformation fault associated with, including: 1) right-lateral displacement up to 1.5 m at the age of minab conglomerate and laxyers of khekoh sandstone and minab alluvium. 2) evidence of reveres faults near with displacement of the cm-scale. 3) kink structures developed by reverse branch of the minab fault in the Miocene Pliocene sediments. 4) folds related to reverse which related to minab fault and happened occurred in the laxyers at the age of Miocene to Pliocene. 5) relating to reverse near minab fault activity some landslide in the minab dam reservoir has been the occurred along that fault. The second part of investigation is permeability of the rock mass and water leakage the reservoir minab fault activity at this stage, the rock mass around dam has been studied in five parts and in each flank the GSI and RQD have been investigated. The results indicate GSI values in a range of 32 to 48 for the total rock mass which are dam contained highly qualitied for block and poured concrete block, which are varied due to litology and joint set number and properties. Also in study fairly consistency for the weathered rock mass the estimated RQD, which from the Deere described commonly are known moderate, and weak, in cases such as crushed fault zones of minab fault rating very low in quality. regarding to obtained RQD for permeability of and volume of water, HC experiment model which is baxsed on for parameter containing RQD, DI, GCD & LPI has been used which result contained : - Estimate of rock mass permeability baxsed on experimental model shows has more permeability for the rock mass effected by minab fault activities in the reservoir and minab fault crush zone. - baxsed on obtained permeability from each part in two flanks dam, and flow volume, can be said that rock mass affected of minab fault and crush zone of this fault can be mast significant places, and also rock mass at the baxse of axis of dam, which has the critical hydraulic gradient is large, and the transfer of significant amounts of water into the river downstream of the dam, are the likely locations and main water leakage. - Influential of flow volume in the reservoir in the maximum water level, according to the permeability obtained by the HC model, and according to maximum permeability (2.93 * 10-6) is equal to 0.062 cubic meters per second, which makes the water leakage 1.98 million cubic meters per year. - Result according to defined permeability (10-5) shows that flow volume in the reservoir in the maximum water level, according to the permeability obtained by HC model, is equal to 0.29 cubic meters per second, which causes water leakage 9.21 million cubic meters per year.