This paper evaluated the ecological security of a typical composite ecological system with the case study of Lu An Wangzhuang mining area in Changzhi, Shanxi Province. Based on the pressure-state-response (PSR) model, the evaluation index system was assumed. According to the structural characteristics of the index system, the weights of the indicators were calculated by Analytic Network Process method (ANP), and weights sensitivity analysis was used to determine sensitive factors which affected the ecological security of the mining area. The evaluation results reveals that: (1) the ecological security integrated index of Wangzhuang mining area showed an increasing trend year by year, from 0.560 in 2006 to 0.712 in 2010. Ecological security became relatively safe in this area after 2009 and responsive actions in recent years played a key role to this change; (2) Due to greater weights and more changeable values, 9 indicators such as GDP increasing rate, Waste water recycling rate, Per capita green area shows relatively sensitivity to ecological security integrated index. More attentions should be paid to insensitive indicators in low level and sensitive indicators which have downward trend in order to further improve the ecological security of this mining area.