对于实际的大口径高功率激光器而言，I/II类角度失谐三倍频系统的谐波转换规律常常偏离理想情况。为了研究其实际的谐波转换规律，以便于指导实际情况的晶体调试，研究了各种非理想条件下，比如1 ns高斯脉冲，不同波面半径和晶体损耗对三倍频谐波转换的影响。研究结果表明：高斯形脉冲的三倍频外效率绝对值比平顶脉冲降低了10%；为了追求最高三倍频外效率，由于受1 ns高斯脉冲和三倍频晶体损耗的影响，二倍频晶体的最佳内失谐角是160 μrad而非220 μrad，二倍频内部效率最佳平均值并非为67%，而是在60%~63%左右为最佳，并且晶体损耗越高，二倍频内部效率的最佳平均值越低；功率密度越高，波面半径和发散角对谐波转换的影响越大。

The harmonic conversion rule of I/II angle-tuned third harmonic gemeration (THG) system will be far away from the ideal rule on actual large-aperture and high-intensity laser facility. To study actual harmonic conversion rule and guide the crystal debugging, the nonideal conditions, such as 1ns Gauss pulse, different wave radius and crystal loss have been studied. It is proved that the THG external efficiency will reduce 10% than flat-temporal pulse. To obtain the highest THG efficiency, the optimal SHG internal tuned angle is not 220 μrad but 160 μrad impacted by 1 ns Gauss pulse and crystal loss. And the optimal second harmonic generation (SHG) internal efficiency is not 67% but 60%~63%. The higher of crystal loss, the lower of SHG internal efficiency. And the higher of 1ω intensity, the greater of infection of wave radius and divergence angle on harmonic conversion.