The parent ions (H2CO+) and the descendent ions (CO+) from higher energy dissociation channel, generated by 2+1 and 2+2 photon resonant excited processes respectively, have been found in the multiphoton ionization investigation on formaldehyde with XeCl excimer laser. No HCO+ ions from lower energy dissociation channel (which are dominant in both electron impact and single-photon ionization mass spectra) appear as a result of state-selective excitation.