The photoionization of acetone seeded in helium is studied by time_of_flight mass spectrometry using a 25 ns, 532 nm Nd: YAG laser with intensity in the range of 1010—1011 W/cm2. Multiply charged ions of Op+(p=2—4) and Cq+(q=2—4) of tens of eV have been observed when the laser beam irradiates the most dense part of the pulsed molecular beam. The intensity and the kinetic energy of the multiply charged ions increase with the increasing of the laser energy. An electron re_scattering and re_colliding ionization model is proposed to explain the appearance of the multiply charged ions under such low laser intensity.