Abstract: Gives the lower limit estimation of response probability based on the method of ordered relations in sample spaces under logistic response model. To estimate the response probability of detonator products, a sensitivity test is always used. The sensitivity data (n i, s i), i=1,2,…,k can be obtained and will be transformed into the ordered relations in sample spaces. Using the theory of ordered relations in sample spaces, the lower limit estimation of response probability is given. Based on this study, the Monte Carlo simulation is given, compared with the result from the method of asymptotic normality, and is applied to the detonator QD 8. Numerical results show that the method of ordered relations in sample spaces can much better estimate the lower limit estimation of response probability under cases of small samples.