Abstarct: According to slake of surface high grade ore deposits Seems that facing strategy of mining industry can be turning to underground mining methods and also tracking and explore the resources and reserves that are not discovered. But another Strategy can be searches in management and optimal utilization of the existing potentials and now extracting mines. Although complex in practice, but this evaluation process can be seen as a combination of management strategy with a critical understanding and assessment of uncertainty and risk from technical, financial and environmental sources. A critical source of technical risk is in the expected ore grade and tonnage. The ability to model and integrate this risk into optimization and planning is of paramount importance and allows a more informed approach to be taken to the valuation of an asset or design and management of a project. During the past few years evolving technologies have allowed direct modeling of technical and geological risk. In this study to investigate the sensitivity of open pit mine design and planning with relation to chances of inherent ore grade, Dardvey Iron ore deposit (One of the sangan deposits, Iran) using conditional simulation methods has been evaluated. For construction of deposit geological model, geostatistical evaluation, optimization of estimated and simulated models respectively used from software’s of Datamine, WinGslib and NPV Scheduler. The obtained results show that the estimated model underestimates total rock tonnage, recoverable ore tonnage, average mill filed grade, pit value and NPV against over all expected values of simulated realizations. The magnitude of the differences for mentioned parameters respectively are 61.89, 11.19, 14.05, 2.83 and 60.53 per cent. However, the total ore tonnage of estimated model against the expected value of realizations show a decrease of approximately 5.4 per cent that it is because smoothing of kriging estimation. A series of plans and cross-sections produced for all ultimate pits of simulated block models and an estimated block model. These plans and cross-sections overlaid that the main conclusions drawn from the analysis of these cross-sections are the following. The walls of pit limit are unstable with relation to grade uncertainty specially the southearth wall that indicates higher levels of grade uncertainty and are main upside potential risk regions. In addition, spread of simulated limits in depth was significant that uncovered by estimated pit limit, so this region can be additional drilling targets. Also, operational cost per recoverable ore calculated for all of simulated models and estimated model that results show an increase of approximately 19.81 per cent for estimated model against the expected value of simulated models in early pits, but in end phases estimated model show an decrease of approximately 2.73 per cent against the expected value of simulated models.