High angle-of-attack flow over a 20° conical forebody was computed with laminar model, Gamma theta transition model and turbulence model to study the flow characteristics. The contour of computed total pressure coefficient, velocity vector and axial vorticity distributions over the cross-flow plane at 30m/s and different angle-of-attack were plotted here for study. Through the comparison of experimental data with numerical solution, we can get that gamma theta transition model is proper to model flows mainly in transitional region. For angleof-attack greater than 10°, the port and starboard primary vortex occur. Each of them has a minimum value of total pressure coefficient and a maximum absolute value of non-dimensional axial vorticity in the vortex core. Both of them vary with the angle-of-attack and the wind velocity in some regular patterns.