This paper uses a variety ways to prepare the gypsum(CaSO4·2H2O) and measured its physical properties, including vertical suction height h, the water velocity u in the horizontal state, the porosity η and the average pore radius. The results show that the way of preparation of the porous medium gypsum has great relationship with its properties. The gypsum is formed by adding some proper water into the CaSO4 , and its porosity is increasing with the increase of the water, but the strength is decreasing. Adding a bit of potassium citrate in the water can improve the performance of the gypsum , and the vertical suction height, the water’s horizontal velocity and the porosity can reach 120 cm, 4.2 mm/min and 69.4% respectively, so the gypsum can be used as the filling materials of the capillary suction liquid core radiator.