研究了对虚共焦非稳腔结构的脉冲TEA CO2激光器远场光束质量进行评价的方法。首先将稳腔TEA CO2激光器加工改造成非稳腔结构；然后从实际设计加工的数据出发，用3种常用形式对其远场光束质量进行理论评价与分析，并与设计的2 kW非稳腔激光器的实测远场光强分布实验结果进行了对比。理论和实验结果表明,非稳腔能够获得接近衍射极限的高质量单模光束，β因子是稳腔的4倍多；在同等功率水平下，采用非稳腔的激光器的远场功率密度是稳腔的19倍；非稳腔较小的遮拦比能获得远场较高桶中功率。实验表明，要全面地预测和评价所设计非稳腔激光器的光束质量，需要根据实际，综合地运用3种形式的理论评价体系。

The evaluation methods for far field optical quality of a TEA CO2 laser with a unstable resonator were researched. Based on the real data of the unstable resonator modified by the stable resonator of a high power TEA CO2 laser, three common theoretical evaluation methods were conducted to evaluate the optical quality.Obtained results were compared with that from the far field optical intensity distribution of a designed 2 kW unstable resonator laser. The analysis and comparison show that the unstable resonator can obtain a near diffraction limit and a high optical quality beam and the β factor is 4 times that of the stable resonator. Under the same power level, the far field power density of the unstable resonator is 19 times that of the stable one. Furthermore, the smaller block factor can obtain a higher power in bucket for the unstable resonator. It is concluded that the comprehensive prediction and evaluation of designed unstable resonator need to synthetically use the three theoretical methods to complete.