Determination test of the reliability of air gap detonation transmission interface was designed through air gap length as variable and testing device were constructed. The reliability of air gap detonation transmission interface composed of including detonator, air gap and detonating explosive in partition initiator was tested and estimated by Neyer-D Optimized method. Results show that the critical functioning length of air gap is 18.76 mm. The reliability of the interface function obtained by interval estimation of p quantile is 0.999925 at confidence level of γ=0.95.