The HMX explosive with particle size of 587.3 nm and precision press loading technique were selected, different sizes of channel were desogned with LZ12. The detonation propagation critical characteristic of superfine desensitived HMX in channel was studied. The results show that the critical size of linear charge is 0.4 mm×0.4 mm, the limit size of linear charge is 1.2 mm×1.2 mm, and critical size of convex charge is 0.5 mm×0.5 mm, when the charge density is 1.77 g·cm^-3.