With time- and space- resolved technique, the time-resolved spectra of the plasma induced by Nd:YAG laser ablating metal aluminum in Ar were recorded, in which, laser pulse energy was set up to 115 mJ and the buffer pressure 10 kPa. The continuum radiation of aluminum plasma was studied. The mechanism of the continuum radiation of the plasma induced by laser ablating aluminum is discussed. Resonantly absorbing continuum radiation was suggested. Bremsstrahlung and compound radiation of electron were considered as main mechanism of continuum radiation. Short after the laser beam getting to the surface of the target, Bremsstrahlung is the primary mechanism of the continuum, during early stage of the plasma involution the continuum radiation derives from Bremsstrahlung and compound radiation of electron; but during late stage the continuum emission only comes from compound radiation of electron. Atom Al selectively absorbs continuum radiation, it leads to the change of the smooth distribution of continuum emission with wavelength under normal condition.