The pressure effects which induce by sound wave propagation in liquid crystal near N-SA phase transition when T → Tc+ has been considered.We have calculated the ultrasonic attenuation coefficient and the dispersion by use of mode-mode coupling theory. It is found that for high frequency the behaviour of attenuation has anomalous divergence, in low frequency limit it's critical exponent is 2.5.When T→Tc+, the theoretical curves are nearly in agreement with experiment results.