双光栅单色仪的透过率函数对转动喇曼激光雷达回波信号的模拟计算、温度反演灵敏度的分析、温度反演公式的选择等具有重要作用。为了研究双光栅单色仪透过率函数的算法，采用一个变量把衍射光斑占出射光纤横截面积的比表示出来，然后利用光斑与光纤横截面是相离、相交还是相切的关系给出了透过率函数，对532nm的双光栅单色仪的透过率函数进行了理论分析与实验研究。结果表明，532nm双光栅单色仪的透过率曲线的中心波长分别为529.0nm,530.3nm,533.8nm和535.1nm,带宽为0.48nm，模拟的回波信号与实测回波信号基本重合,双光栅单色仪透过率函数的计算方法是正确的。

Transmission function of double grating monochromator plays an important role in rotational Raman lidar’s simulation calculation of echo signal，the analysis of temperature inversion sensitivity，the selection of temperature inversion formula and so on. In order to study algorithm of double grating monochromator transmittance function, the sectional area ratio between light spot and output optical fiber was expressed by a variable. And then transmission function was given by the relationship of phase, intersection, tangent between light spot and output optical fiber cross section. 532nm double grating monochromator transmission function was analyzed in theory and verified in experiments. The results show that, central wavelength of 532nm double grating monochromator transmission curve is 529.0nm,530.3nm,533.8nm and 535.1nm respectively and the bandwidth is 0.48nm. The simulated echo signal and the measured echo signal are basically consistent. The calculation method of double grating monochromator transmittance function is correct.