Abstarct: It has been about 4 decades that application of optimization algorithms in designing mines have come to vogue. Most of the progresses of these algorithms have been on the open pit mining. Unlike open pit mining, growth of such algorithms on the field of underground mining have been to slow, due to high variety of underground mining methods, complexity of economic modeling of mining limit and using simlpifying assumption. In order to determine the optimum underground mining limit, a new algorithm called Stope Optimiser Algorithm (SOA) was designed. In this algorithm, the optimum limit is determined in a level considering given constraints. Also in this algorithm, constraints like minimum and maximum dimension of stope, minimum and maximum level height of stope, leveling constraints and minimum width of rib pillars are considered. To consider mine designinig operations unanimously, an algorithm called Mining Limit Optimiser Algorithm (MLOA) have been used. In the MLOA algorithm, after determining the number and location of all the probable levels, the SOA algorithm is used to determine the number, dimension and location of stopes in any probable level. At last by determining the obtained value of probable mining area, all of these limits are compared and an optimal arrangement of number and location of levels, together with stope limit determination in every level is selected as output of the MLOA algorithm. Also, a computerized program have been designed in MATLAB, that determines mining limit, baxsed on MLOA algorithm, after entering income and cost block models and other technical and economical factors and finally, a tridimensional image of the optimum limit of stopes and levels is obtained as the output of this algorithm.