  It is proved in the manuscript that as long as the proper coordinate
transformation is introduced,, the equations of geodetic lines described in
curved space-time can be transformed into the dynamic equations in flat
space-time, that is to say, the Einstein theory of gravitation and other
theories based on the curved space-time can be identically transformed into
flat space-time to describe. As an example, the Schwarzschild solution of the
spherical symmetry gravitational field is transformed into flat space-time to
study. The results show that there exists no any singularity in the all
processes and the whole space-time including at the point r=0. So it seems more
rational to discuss the problems of gravitation in flat space-time.
