A total of 100 trajectories for the photodissociation, CH3CHO --> CH4 + CO, on the S-0 potential surface have been calculated using the direct ab initio molecular dynamics method at the RMP2(full)/cc-pVDZ level of theory. The energy, distributions for the relative translational energy, the CO internal energy, and the CH4 internal energy were calculated to be 28, 20, and 51%, respectively. It was predicted that the product CO is highly rotationally excited but vibrationally almost not excited; on average, the rotational and vibrational quantum numbers were 68.2 and 0.15, respectively, which qualitatively agrees with the recent observation of Gherman et al.