Abstract：In this paper the cubic spline function was used to describe the formation interface,the Thomsen parameters was utilized to describe velocity anisotropy,then the layered anisotropy model was established and the classic test firing method was used to realize VTI medium ray tracing.In this paper estimation of test firing angle,calculation of phase velocity and group velocity,processing of transmitted and reflected waves,reflection coefficient calculation and other key techniques were discussed in detail,the expressions of the incidence angle for VTI medium,the transmission phase angle,and the reflection phase angle were derived.The VSP ray tracing test shows that the expressions of the incidence angle for VTI medium,the transmission phase angle,and the reflection phase angle were accurate,the algorithm could converge fast with high precision,its dynamics calculation was accurate,so with its excellent universality it can be applied to the TI medium.
