Theoretical and experimental study on the polarization modes are performed on copper vapour lasers. The properties of polarized pulsed light are explored and the results show that the average polarizability of pulsed light is decreased with the increase of output power within a certain power range, whereas it is increased with the shortening of. the cavity length, and increased with the increase loss ratio M. These results are verified experimentally, and an average polarizability of 97.6% has been obtained for the laser output.