The window and its coating of the Raman cell are easily damaged by the laser beam with very high power laser. A novel Raman cell without solid windows is designed. Two gas switches are used at two ends of the Raman cell, a gas mixture with a density very close to the air is used as Raman medium. This gas mixture will not diffuse very fast after the gas switch is open. So the Raman conversion can be obtained without solid windows. The effects of gas flow during the gas window operation on the Stimulated Raman scattering are investigated.