A 14CO2-12GO2 isotope laser has been developed and 80 laser lines were measured. 40 lines originated from lasing transition of 001-(100, 020), band of 14CO2 and the strongest line output power was over 4.0 W. The competition effect between isotopes were experimentally observed and domination of lasing radiation of 14CO2 were found even if the content of 14CO2 was less than 12CO2.