Abstract: The following conclusions were induced through researching uncertainty character of response surface method and interval variable and underground structure:(1) Calculated result of static response for structure with uncertainty by response surface method was very accurate;(2) Interval variable was very suitable to express uncertainty of mechanical response and mechanical and physical parameters of underground structure,but it was very difficult to acquire analytical equation of structure function.Therefore,response surface method based on statistics was improved.Formation of response surface function,test and design methods and fitting procedure of analytical equation of response surface function were put forward based on interval variables.According to character of independent variable in the function,solution of value field for function whose independent variables were interval variables was studied.Based on analytical equation of response surface function,the present study was focused on solution of value field and concrete calculation procedure of response surface function in which same independent variable appeared in equation repeatedly.Non-probabilistic reliability analysis of response surface method based on interval variable was established.A practical engineering example was analyzed by the abovementioned method,and its validity and feasibility was shown.