The utility model relates to a different moisture content shaked out critical pressure less than experimental apparatus after evaluation open hole completion oil well went out water, the device characterized in that: the high 50cm of autoclave, diameter 40cm, experiment core diameter 14cm, high 35cm, the middle center -through hole who is 2.5cm of rock core, as the simulation wellbore hole, axle load controlling means changes the axial pressure of piston to the rock core, rubber packing pad on the messenger, rubber packing pad is sealed with the rock core down, profit mixing ratio passes through the quantity of water regulation ware in the experiment, oil quantity adjustor adjust, constant voltage equipment adjusts the pressure that the profit mixture got into the autoclave inner chamber, and can export constant pressure, data collection card gathers the inlet pressure sensor, the pressure and the laser particle analyzer measuring sand content of outlet pressure sensor, sand content in the laser particle analyzer real -time measurement oil water mixture, be greater than at 0.5 per mill o'clock when the sand content, the rock core takes place to destroy, the inlet pressure sensor was poor for shaking out the critical pressure promptly with the pressure difference of outlet pressure sensor this moment.