Abstract: In order to simulate work environment of high dam concrete and effects on the mechanical properties of concrete due to high seepage pore water pressure, standard concrete samples are immersed into a high water pressure container and high hydraulic gradient is produced in testing samples. The concrete mechanics and physical properties studied in the paper are included strength, young’s modulus, water content and wave velocity. The effects due to different water pressure in the container (concrete pore water pressure), time, concrete grade and aggregate maximal grain size are considered in experiments. Experimental scheme is designed by an orthogonal experiment design method, thusly, 28 groups of experiments for the studying effect of compressive strength, water content and wave velocity, 9 groups for tensile strength are obtained. The study shows that the lost rates of concrete compressive and tensile strength, young’s modulus are gradually increased with the increase of pore water pressure. The significance test shows that pore water pressure, grain size and concrete grade are significance to compressive strength. Under same pore water pressure, the lost rates are increased with increase of grain size and reduction of concrete strength. The water content relates with pore water pressure, and concrete grade. The water content of sample is increased with increase of time and reduction of concrete strength. The wave velocity of concrete sample shows a fluctuation character with increase of pore water pressure.