Abstract: The present paper covers the theoretical analysis and numerical computation of the acoustic wave in the fluid-model bore-hole and it cones to the significant conclusion that the full wave of the inner well consists of gliding p wave , normal wave and leaky wave. This paper demonstrates the existence of the normal mode , it has been made clear that there is not the normal mode under the situation of the fluid-solid mode of slow stratum , and the popularized conception of slow stratum has been obtained and the range and the rule of leaky mode existence have been found.

Key words: polar point, branch point, leaky model, Stonely wave