The direct laser initiation of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) doped with aluminum nanoparticles was conducted using a short laser pulse of Nd:YAG (1064 nm wavelength, 14 ns duration) through a 1 mm diameter optical fiber. The effects of aluminum nanoparticles on thermal stability, light absorption, and laser initiation energy were investigated. Results revealed that the aluminum nanoparticles significantly enhanced the absorption of light and decreased the laser initiation energy. The laser initiation energy, which was higher than 1000 mJ for an undoped CL-20, could be reduced to 80, 40, 30, 30, and 20 mJ by adding 0.2 %, 0.5 %, 1.0 %, 2.0 %, and 5.0 % aluminum nanoparticles, respectively. When a short pulse laser was radiated on the surface of the explosives, the aluminum nanoparticles absorbed the laser energy, heated, and reached high temperatures, resulting in hotspot formation and detonation. The direct laser initiation of doped CL-20 with a short laser pulse and a low energy through an optical fiber would contribute to the manufacture of small, safe, and reliable laser detonators.