This paper studied the revisions to Einstein’s theory of relativity, introduced the concept of “size mass” and put forward the new relativity mass-velocity formula; and then it put forward Liu’s Cosmological Model, analyzed the nascence, birth and development of the universe, obtained the Universe Moving Equations, and calculated the present universe’s parameters; and it analyzed the conditions that a celestial body occurs the similar big bang and the model that the Galaxy occurred the second big bang. The results show that at its nascence, the universe was a big neutron of which the temperature was 8.876×1012℃, the radius was r0=4.84×1011m and that was at rest, under the action of temperature energy (heat energy) releasing, the center of this big neutron generated repulsive force to the surrounding. Under the common action of the repulsive force and gravitation, at the moment tb=6.77×10-5s, the Big Bang occurred. Since the Big Bang, most celestial bodies have been leaving the center of the universe and spreading around with velocities above 0.47c, and the universe is constantly expanding. When an object moves relative to the absolute frame of reference, its three-dimensional size will shrink by the same proportion. The four-dimensional Minkowski space-time is meaningless. The size mass of a system is reduced, if its temperature is maintained unchangeable, then its energy will be correspondingly reduced, and the other system accepts an increase of size mass, if its temperature is maintained unchangeable, then its energy is correspondingly increased.