The copper ion laser supplies interesting CW UV emission in the region 248 - 270 nm. It is possible to realize VUV (-160 nm) laser oscillation in the copper ion laser. Its discharge characteristics, laser gain and output performance in dependence on the operating conditions have been investigated. A UV laser gain of 4.72%/m and a quasi-CW power of 700 mW without the optimum of the output coupling have been measured. The processes in laser plasma can be described and the experimental results were good explained with a theoretical model presented by the author.