The altitude characteristics and velocity characteristics of three types of solid ducted rocket, which are choked solid ramrocket with fixed mass flow rate of fuelrich gas generator, unchoked one and the one working under fixed mass ratio of air to fuel, were numerically studied. The results show that the performance of the unchoked ducted rocket is superior to that of the choked one. When the gas generator is loaded by fuel-rich propellant with high exponent, the unchoked ducted rocket can almost be worked under fixed mass flow ratio of air to fuel.