In the framework of general relativity, systematically deal with the problems of galaxy formation and evolution. Einstein’s equation of gravitational field is first improved, space-time is proved to be infinite and its expansion and contraction are in circles, the singular point of big bang didn’t exist, Besides, it is disclosed that galaxies or celestial bodies form from unceasing growth but not the assemblage of existent matter after big bang, new matter continuously creates in the interior of celestial bodies depending on the work done by the negative pressure, and in the same time celestial bodies, galaxies and space synchronously enlarge in accordance with Hubble expansion, cosmic density and pressure keep unchanged.

background coordinate system, convex lens effect of space-time expansion, negative pressure