A Q-switched Nd: YAG laser (with a wavelength of 532 nm and a pulse width of 15 ns) was used to ablate hexahydrol, 3,5-trinitro-l,3,5-triazine (RDX) in the air. The plasma emission spectra were recorded by an intensified charge-coupled device (ICCD) camera. The results showed that the plasma existed in the process of laser ablation of RDX. In the ultraviolet area, the main spectral lines were C I (187.46 nm and 223.01 nm), C II (323.1 nm) and N II (243.72 nm and 332.9 nm), while the dominating emission lines in the visible area were N II (393.9 nm and 454.7 nm), O II (490.75 nm) and O III (401.2 nm). Under experimental conditions, the intensities of the main peaks grew obviously with the increasing of the pulse delay, but laser energy didn’t have so much effect on the spectra. The ionization of the air almost did not influence plasma emission lines of RDX.