The mass spectra of a series of cycloketone molecules, cyclopentatione (CPO), cyclohexanone (CHO), cycloheptanone (CHPO), and cyclooctanone (COO) are measured in a 788 or 394 nm laser field with 90 fs pulse duration and the intensity ranging from 5 X 10(13) W/cm(2) to 2 x 10(14) W/cm(2). At 788 rim, a dominated parent ion peak and some weak peaks from the fragment ions CnHm+ are observed for CPO and CHO (a ratio P+/T+, the parent ion yield to the total ion yield, is 81.6% and 52.6%, respectively). But the extensive fragment ion peaks are observed with the greatly reduced parent ion peak for CHPO (P+/T+ = 5.5%) and that are even hard to be identified for COO. These observations are interpreted explicitly in the frame of the significant resonant effect of their cation photoabsorption on ionization and dissociation of these molecules. The present work also suggests that a nonadiabatic ionization occurs with a nuclear rearrangement due to the H movement in these molecules during the ionization in an intense fermosecond. laser field.