Abstract: Spark test apparatus is testing equipment of intrinsically safe electrical products about spark test, its research and application are an important link of intrinsically safe parameter determination and testing technology development of underground coal mine. Through the analysis of the influencing factors of the reliability sensibility of thermal ignition of small component, based on the uncertainty of different basic variables, the paper conducted curve fitting of the relevant inputs, proposed the approximate process of binary regression analysis based on the covariance of the relevant inputs to correct the sensibility. In order to verify the effectiveness and the accuracy of algorithm of the reliability sensibility, sensibility tests was conducted for several times. The simulation results indicate the proposed research method is helpful to optimize the assessment process and improve the verification efficiency.