Blunt rocket sled experimental model with two-tracks and two ranks of vehicles was numerically simulated based on un-structured grids. The results were compared with free-stream situation of blunt. It is showed that there is a higher pressure domain at the low surface of blunt in experimental model. The pressure becomes bigger and the point of the highest pressure of low surface moves backward as the Mach number raising. Trailing vortices of blunt are unsymmetrical in experimental model because of the ground effect and the interaction effects. On the whole, it is suggested that the sensor be installed away from ground where 0.2<x/L<0.4.