Abstract：AVO analysis is based on Zoeppritz's equation. The odevity of both converted wave and unconverted wave is generally demonstrated by using Zoeppritz'sequa- tion. The power series expression of Zoeppritz's equation is offered，by which we can obtain any approximation of Zoeppritz's equation. The power series expression of Zoeppritz's equation has some advantages such as simplicity，high accuracy and separation of elastic parameters from incident angle，reflection angle or transmission angle，so that it is applicable to the case where elastic parameters show great difference at the both sides of an interface,and particularly to quantitative and theoretical AVO analyses. It will find wide applications. AVO information volume within the critical angle is estimated,which is the direct use of the power series expression.
