建立了非稳腔激光束通过大气湍流随机相屏传输至远场焦平面上的光斑强度分布模型，并考虑CCD像素单元对激光能量的离散化积分采样及探测噪声的影响，以峰值斯特雷尔比Rs、环围能量斯特雷尔比Ree和光束质量因子β作为评价远场光斑质量的指标，利用蒙特卡罗法研究了在不同信噪比(SNR)和光斑分布形态情况下，采取四种不同阈值去噪方法对远场光斑质量评价参数计算精度的影响。结果表明，足够的测量信噪比是保证光束质量测量精度的前提，在测量信噪比和光斑分布形态给定的情况下，采取阈值为CCD背景噪声均值，同时保留随机噪声起伏的去噪方法是较为合理的选择。

The far-field light intensity model of annular plane beam through Kolmogorov atmospheric turbulence is presented, and both the discrete sampling of CCD pixel and detection noise are considered as well. The parameters of peak Strehl ratio、encircled energy Strehl ratio and beam quality factor are taken to evaluate far-field spot quality, and the Monte Carlo method is used to analyze the influence of four kinds of threshold method on calculation results of far-field spot quality when signal noise ratio (SNR) or turbulence strength is different. The results show that accurately measurement results of far-field spot quality are premised on adequately high SNR; if the SNR and turbulence strength are fixed, the threshold method of subtracting average background voltage of CCD and reserving random noise is the better choice to obtain the higher calculation accuracy of spot quality.