Abstract: The law of pressure spread of elastic fluid unsteady flow in different low states is derived by using the steady state replacement method. Pressure spread in spherical flow is the fastest among the spherical, radial and linear flow states, and that in linear flow is the slowest among them. The time of pressure spread in linear flow is 2 times as fast as radial flow, and that in radial flow is 1.5 times as fast as spherical flow, when distances of pressure spread are equal among them.

Key words: pressure, travel time, percolation