We have investigated Raman beam combination to improve the beam quality of a XeCl excimer laser. It was verified theoretically that the near diffraction-limited Stokes light could be obtained with abberated pump beams. The selection of Raman gas media was then discussed on steady and transient pump pulse conditions. Experimentally, we studied the Raman combining in H2 with two pump beams.The near diffraction-limited Stokes light was amplified intensely with unchanged far field distribution,resulting in a brightness increase of 3000 times. Finally we discussed the amplified spontaneous emission in a Raman amplifier.