People have carried on the extensive researches on the superluminal velocity in experiment and theory, but it is difficult to reach consensus. The biggest problem here is the theory of relativity, which shows that when a object (a matter with mass) reaches or exceeds the speed of light, whose relativistic factor will become infinite or imaginary numbers, so it is impossible to superluminal motion. In fact, although relativity is quite correct quantitative theory, but it has certain limitations. Relativistic effects are the vacuum effects, not the substantive effects. Relativistic physical quantities are only apparent physical quantities expressed through ether(physical vacuum). The substantive physical quantities of an objects are proper physical quantities, which will not vary with the velocity. Moreover the ether in superluminal velocity would lose superfluidity, and thus the superluminal velocity is beyond its scope of application of relativity. Therefore studying superluminal velocity need not scruple the restriction of relativity. Human superluminal activities will involve gravitational shielding, superluminal communication and other supertechnologies.