Abstract: This article selected thirteen evaluating indexes which reflecting the coal mining conditions based on extension theory,and determined classical domain and joint domain of each index.The extension evaluation model of comprehensive evaluation for coal mining condition was built.Taking comprehensive correlation degree as a principle,this model not only can avoid subjectivity of evaluation model but also can reflect the disparity between security rank of coal mining condition and other different ranks by eigen value of the security rank.Practice results showed that this method was simple,reliable,practical,and it provided a new method to achieve comprehensive evaluation for mining technology condition.