In this work an improved set of small-scale gap tests was applied to measure the shock sensitivity of 13 explosive compounds, and a Mn-Cu manometer was also employed to measure the output pressures of shock waves passed through aluminum gaps with different thicknesses to draw a standard curve. The critical initiation thicknesses of aluminum gaps of different explosive compounds (244 shots in total) were treated according to statistical method, and the Mulliken charges of nitro groups, bond dissociation energies of X-NO(2) (X = C, N), resonance energies, and ring strain energies of these explosive compounds were calculated with the means of DFT/BLYP/DNP calculations and homodesmotic reactions designs. Genetic function approximation was used to construct a relationship between the critical initiation thicknesses of aluminum gaps of different explosive compounds and their forementioned molecule structural parameters.