We have studied two batches of photovoltaic HgCdTe detectors irradiated by CW band-in laser, and discovered, two different over-saturation phenomena. It is shown that the over-saturation phenomenon associated with the open-circle voltage signals which decreases with increasing light intensity is of universal existence in the PV HgCdTe detectors irradiated by intense light. The regular and special phenomena of PV HgCdTe detectors under intense light radiation are definite and obvious. The generation conditions for the two typical over-saturation phenomena are analyzed in terms of the equivalent circuit model. These two kinds of over-saturation phenomena have been numerically simulated. Numerical results are in good agreement with experimental data. It is found that the two generation mechanisms of the over-saturation phenomena of PV detector under irradiation of the above-band gap laser do exist. One is the increasing dark current due to thermal effectm, and the other is the leak current due to the bugs in the detector material.