Abstract: Based on petrophysical parameters of 31 water saturated limestone samples from the right bank of Amu Darya，
Turkmenistan，the Castagna polynomial and exponential relation of P-wave velocity and density was evaluated. According
to the result，the predictive densities by Castagna exponential relation are bigger than real values with major prediction error.
However，the Castagna polynomial relation can better reflect the character of P-wave velocity and density；besides，its fitting
accuracy increases gradually along with the increase of the confining pressure. The result is of great benefit to reservoir
prediction research，and has important theoretical and practical value.

Key words: limestone, velocity-density relation, Castagna relation, Gardner relation