This paper introduces to the experiment results of a impact of the delay time changes between spark pin UV preionization and main discharge on the optoelectronic conversion efficiency in a TEA CO₂ laser.By using different inductance values in a discharge circuit,the delay time can be changed.The results indicate that the optoelectronic conversion efficiency has an optimal point when delay time is changed from 200 to 600 ns.In the same injected energy the single pulse output is increased from 24.0 to 45.6 J and optoelectronic conversion efficiency from 8% to 15% respectively.The highest conversion efficiency reaches 17% after further parameters optimization.