Strength and dilatancy of plastic concrete were studied using two kinds of true triaxial compression tests, and lateral pressures were constant in one kind of test, and they increased with axial pressure in the other. The result shows that strength of plastic concrete increases with lateral pressure in the first kind of test, and when σ3 is constant, σ1 increases with the increase of σ2. There is dilatancy for plastic concrete in the first kind of test; onset of dilatancy increases with the increase of σ2. Strength of plastic concrete increases greatly in the other test, to the extent of 4.06.0 times to that of the uniaxial compressive one. There is no dilatancy in the true triaxial compression test with constant lateral displacement; and volume of plastic concrete specimen decreases with the increase of axial pressure. Bulk strain increases with the increase of the initial lateral pressures.