Abstract: The process of proposition of Schwarzschild solution of gravitational field of spherical symmetry is reviewed. The physical meaning of gravitational radius is illustrated. The development of concept of black hole is introduced. The non-strangeness of spherical space-time of gravitational radius and space-time structure in gravitational radius is analyzed.

Key words: Sehwarzschild metric, gravitational radius, event horizon, black hole, space- time strange point, cone of light, time-like interval, space-like interval