The mass selected MPI spectra and time of flight mass spectra of acetone in the region of three photon resonant with 3d and 4s Rydberg states were obtained using multiphoton ionization time of flight mass spectrometric technique. Two relative strong ion peaks were assigned to CH 3CO + and CH + 3, and weak ion peaks assigned to C +, CH +, CH + 2, CHO +, no parent ion peak was observed in the wavelength region. Mass selected MPI spectra of these main cations exhibited the same feature, could be attributed to (n 0, 3d) and (n 0, 4s) Rydberg transitions. We also measured the dependence of fragmental ratio of each ions on laser intensity and laser power index of total ions. Based on the experimental results, the multiphoton ionization dissociation mechanics of acetone was discussed. The MPI of molecular ions model was analyzed with rate equations. Using simple three energy system model, we also estimated three photon absorption cross section of n 0→3d Rydberg transition of acetone.