Inter-stage-turbine burner(ITB) with no radial vane cavity and five different kinds of radial vane cavity shapes three-dimensional combustor model on two phase combustion flows are simulated by utilizing a computational fluid dynamics software together with [WTBX]k-ε[WTBZ] model and simplified PDF combustion model. Velocity field, temperature field and overall performance of different kinds of ITB models are compared and analyzed. The result shows that the different radial vane cavity shapes differ on the velocity and temperature field in the radial vane cavity, and then have an influence on the combustion completeness of the rich burn products and outlet temperature. By changing the radial vane cavity shapes, ITB can obtain higher combustion effeciency and outlet temperature, smaller pressure drop and better species concentration standard.