The ignition delay times and special spectral intensity of aluminum nanopowders reacting with propylene oxide were investigated by fast spectrum system triggered by synchronous shock light singles, and the ignition mechanism was presented from those data. X-ray diffraction (XRD) spectrum indicated that aluminum nanoparticle produced by plasma method has been oxidized for its high activity, X-ray photoelectron spectroscopy (XPS) of sample revealed that there is 3 nm oxide layer on its surface. XPS of the products showed that the oxide layer thickness will increase with the increasing shock wave strength. AlO(464.8 nm) ignition times investigated by monochromator revealed that aluminum nanoparticle will be equably distributed in propylene oxide vapor for increasing shock wave strength to increase its heating surface and heating rate, and shock wave will easily crack the 3 nm oxide layer on aluminum nanoprticle present chance for core active aluminum to react with oxygen atome and containing-oxygen molecule in the reaction system to ignite.