AVO technology has become an important means for petroleum exploration after decades of development. In the aspect of finding heterogeneous reservoir, AVO technique plays an irreplaceable role compared with other methods. This paper analyzed the AVO characteristics of the lateral variable small-scale body through wave equation finite difference numerical solution method, and discussed the influences of size variation and speed change of lateral smallscale body on the reflection coefficients. The least square method was used to fit the relations of the reflection coefficient difference with scale body width and scale velocity. The result of error analysis combined with test data shows that the error between fitted formula and the experiment data is less than 0.5%, which indicates the influence of small-scale body width and elastic parameters on the reflection coefficient. The formula can be used to predict the size of small-scale body and rock elastic parameters through AVO abnormalities, and provide protection for the validation of the exact expression of reflection coefficient with velocity change of transverse small-scale body.