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In this research, three dimensional grain burn-back of solid rocket motors is simulated based on level set method and its accuracy is increased according to marching cube algorithm (MCA). To that end and according to requirements of level set method, grain burn-back is simulated during three steps included grid generation, distance function determination, and calculation of burn-back parameters. In this article, with focus on last step, we will compare strengths and weaknesses of grain burn-back analysis for common methods such as captured cell, three dimensional cut cell, sectional, and Heaviside Delta Dirac and in following, we introduce and run MCA. In order to validation, firstly three simple grains such as cylindrical, quad and hexahedron are considered and the performance of capture cell, 3D cut cell and sectional methods are compared with MCA in terms of accuracy and CPU time. Then, to evaluate the new method facing complex and practical grains, burn-back results of conocyle and NAWC N.13 grains is compared with MCA and heaviside/dirac delta methods. The obtained results show that MCA has a better performance at CPU time and accuracy.