Laser spot in far field when the flattened Gaussian beam propagating through turbulent atmosphere is simulated and analyzed. The phase screen is utilized to describe the turbulence influence to the propagating laser beam. Results show that when beam propagating through weak turbulent atmosphere, short term laser spot is made up of a small dark spot inside and an irregular light spot around, and the light spot breaks up and intensity distribution become messy and disorder when turbulence gets stronger. For long term laser spot, if the turbulence is weak, the laser spot is regular and there is a dip in the center of the intensity distribution, and strengthen the turbulence can make the spot changed to ellipse but the intensity distribution is similar to Gaussian distribution and the dip in the center disappears. For the beam in this paper, when the turbulence strength is C2n = 10 -16 m-2/3, laser spot center varies in the scope [ -7. 5 mm,7. 5 mm] in x direction and [ - 10 mm, 10 mm] in y direction. And standard deviation of spot center increases when the turbulence strength increases and standard deviation of spot center of flattened Gaussian beam is smaller than Gaussian beam for a fixed turbulence.%由于理论研究和实验研究的局限性,用随机相位屏描述湍流大气对激光束的影响,模拟了平顶高斯光束经湍流大气传输时的远场光斑,并进行了统计分析.结果表明,平顶高斯光束经弱湍流大气传输时,短曝光光斑由中心小暗斑和外侧不规则的亮斑组成,湍流增强使光斑破碎,光强分布杂乱无章；对长曝光光斑而言,弱湍流情况下,光斑形状规则,光强分布存在中心凹陷现象,湍流增强使光斑变为椭圆,但光强变为近似成高斯分布.对于本文的参数值,湍流强度为C2n=10-16 m-2/3时,光斑质心沿x和y方向分别在[-7.5 mm,7.5 mm]和[-10 mm,10 mm]随机变化,湍流增强使质心漂移标准差变大,同一湍流情况下,平顶高斯光束质心漂移的标准差要比高斯光束小.
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