A new method is described to predict shock sensitivity of CaHbNcOd explosives without using any experimental data. It can determine shock sensitivity based on small-scale gap test as the pressure required to initiate material pressed to 90%, 95% and 98% of theoretical maximum density. Three essential parameters would be needed in the new scheme which contain a + b/2 - d, the existence of alpha-C-H linkage in nitroaromatic compounds or N-NO2 functional group and difference of the number of amino and nitro groups attached to aromatic ring. Predicted shock sensitivities in some well-known explosives have a root mean square (rms) deviation of 3.97, 4.02 and 5.89 kbar of experiment to initiate pressure of material pressed to 90%, 95% and 98% of theoretical maximum density, respectively. (c) 2006 Elsevier B.V. All rights reserved.