Abstract: It is an effective way to obtain high convergent compression of fuel with a shaped pulse driven implosion. The hydrodynamic process of the gas capsule compression with a single radiative pulse drive is divided into four phases: shock compression, nearly isentropic compression, compression and expansion with temperature reduction. High density will be achieved mainly through the adiabatic process. By variating the end time of first step pulse, the appropriate two-step shaped pulse drive is found, which will obtain higher density than the single-pulse drive. The simulation shows that the shock produced by the first step pulse compresses the gas fuel many times, meanwhile the pressure in the fuel improves. Hence the second shock into the fuel is so weak that scarcely any entropy increases，an