折射率是基于Mie理论的前向散射法颗粒测量中的重要参数。为了减小颗粒测量误差，在Mie理论、Debye级数展开以及夫琅禾费衍射理论基础上，分析了相对折射率对散射光能分布的影响方式，揭示散射光能分布宽度随相对折射率的变化呈周期振荡特性，并得到该振荡的经验公式；解释了散射光能分布随相对折射率变化的原因，实验验证结果表明，散射光能随相对折射率变化呈周期振荡特性，振荡周期为π，振荡曲线上极小值对应反演结果更接近标称值。因此，在实际测量中，应尽量选择分散介质，使相对折射率对应的散射光能分布宽度处于振荡曲线的极小值点。

Refractive index is an important parameter in the method of particle measurement, which is based on forward light scattering with Mie theory. In order to minimize the errors of the particle size measurement, the effects caused by relative refractive index are studied with Mie theory and its Debye series expansion as well as the Fraunhofer diffraction approximation. Numerical calculation reveals that the width of distribution of the scattered light energy shows oscillating properties periodically along with variation of the relative refractive index, which can be described with the empirical expressions. The cause of the scattered light energy distribution changing with relative refractive index is introduced as well. Experimental results show that the forward scattered light energy behaves in a periodical oscillating way along with variation of the relative refractive index and the period of oscillation is π. The inversion results, which are related to the minimum points of oscillating curve, are closer to the nominal value. So, it is necessary to make the width of the distribution of the scattered light energy correspond to the minimum points on scattering light signal oscillation curve by choosing dispersion with proper refractive index in practice.