Abstract: The rough set and the Monte-Carlo index score method were used in this paper for objective evaluation of oil depot safety. The catastrophe progression theory was mainly used to achieve non-weight objective evaluation. Because the catastrophe progression method has requirements on numbers of evaluation indexes, the rough set theory was used to reduce indexes for index layer with excess numbers of indexes. The following methods were used to perform the evaluation during the expert marking, the score interval, the score distribution, and exact scoring, then Monte-Carlo simulation was utilized to get the random score for the given interval or distribution, to achieve the objectivity of index scores. Finally, multiple evaluation results of catastrophe progression where the Monte-Carlo method was used were gathered and then analyzed to get the evaluation grade. The method is feasible and proved to be useful by practical examples.