An experimental investigation into laser ablation of secondary explosives, cyclotetramethylene tetranitramine (HMX), has been carried out by using a solid-state laser at the wavelength of 1064 nm. The ion particles of decomposition were detected by using a time-of-flight mass spectrometer. Possible attributions of both negative ions and positive ions were obtained. Some obvious peaks were found at m/z = 18, 28, 46, 60, and 106, corresponding to H2O, CO/N2/H2CN, NO2, CH2NO2/N2O2, and N(NO2)2/CH2(NO2)2, respectively. According to the distribution of the particles, three possible pathways were proposed to explain the process of particles. The results may shed some light on the possible decomposition mechanism of HMX under laser initiation.