复杂蜃景通常表现为在竖直方向上同时呈现3个以上的正立或倒立、拉伸压缩交替、扭曲的像.本文首先通过物理实验复现了这种复杂的光学现象，探究了蜃景随观测距离的变化；然后通过数值模拟定量分析了蜃景的变化规律.结果表明：蜃景的个数、位置和形状会随着观察者与介质的距离、介质折射率梯度以及介质厚度的改变而改变，其中倒立蜃景的压缩程度和出现的初始距离分别与介质梯度呈正相关和负相关，而正、倒立蜃景的间距与介质厚度呈负相关.

 Fata Morgana phenomena are usually presented in the vertical direction with more than three mirages at the same time, which are upright or inverted, alternating tensed and compressed, and distorted. In this paper, the complex optical phenomenon is reproduced by physical experiment and the variation of mirage with observation distance is explored. Then the variation law of mirage is analyzed quantitatively by numerical simulation. The results show that the number, position and shape of the mirage vary with the distance of observer, gradient of refractive index and thickness of the medium. The compression ratio and initial distance of the inverted mirage are positively and negatively correlating with the gradient of the medium respectively, while the distance between upright mirage and inverted mirage is negatively correlating with the thickness of the medium.