Abstarct: Along with the development of technology, the low grade reserves are accepted as economical reserves. Nowadays high demand of raw materials and limitations of deposits, have forced us to extract orebodys more accurately and it requires a high attempt to reduce ore losses in mines. Jajarm deposite is one of the biggest Bauxite deposite in Iran and it is placed at north-east of Jajarm city in Khorasan-e-Shomali province. Because of the high stripping cost of Golbini II mine (one of 13 mines in Jajarm deposite) there is no extraction in this mine. According to the previous underground experiment of mine 3, open pit-underground limit of Golbini II is studied. Determining optimum pit depth (open pit versus underground limit) of deep orebodys and possibility of open pit and underground extraction is one of the first decisions that should be made during designing process. In this thesis, by studing seven scenarios, openpit - underground limit of Golbini II mine of Jajarm bauxite mine is determined by Nilsson method. The objective of the model proposed by Nilsson is to choose a pit depth that will maximize the Net Present Value of orebody (both openpit and underground methods). In order to provide input data of Maxipit software, the mine reserves were initially estimated by using Datamine version 2.1 software. It estimated that, mine reserve is 4317984.375 tons (Kaolan, Shale and hard Bauxite) with mean grade of 41.47 percent. Seven geological models with bottom level of 1040, 1060, 1080, 1100, 1120, 1140 and 1160 for hard bauxite are designed. Firstly, the geological models of different scenarios were imported to Maxipit and after cost, price, slope and time settings the fourth scenario (1100 level) was chosen as the optimum limit of Golbini II mine.