Experimental results is presented which show that at the pumping level of 5W, when the beam divergence of copper vaper laser reduces from 8 mrad to 1 mrad, the outpnt power of the dye laser pumped with it will be doubled or more. Further improvement of divergence, however, can only result in slight increase of effcency of the dye laser. This conclusion is in good agreement with the simple analysis of geometric optics. Thus, injection locked unstable resonator is the best arrangement for copper vapor laser as pumping source for dye lasers.