Abstract: The volumetric strain observation of sandstone and plastics under quasi-hydrostatic pressure with 0-3.72GPa is presented in the paper. There are two ways of transmitting pressure, liquid and solid ones. The observes data with low pressure from solid transmitting way are checked by that from liquid one, which leads correct results. The effect of friction of transmitting medium on inner pressure in solid transmitting test is discussed in detail, and the extent of error is given. With analyzing experiment results, the option standard of transmitting medium for the test of solid transmitting pressure is obtained.