研究并给出了参考光束型激光多普勒测速仪中计算信噪比的一般公式，并进行数值模拟，分析了光斑尺寸和探测器孔径对信噪比的影响；同时给出多普勒电流的计算公式，并从理论上分析了参考光束与信号光束的空间位置关系对多普勒电流的影响。理论分析及数值模拟表明，信噪比是参考光光强的增函数，但当参考光光强达到一定值时，信噪比增加的非常缓慢，趋近极限值ηI_s/(hνΔf )；两光束艾里斑尺寸相当时，信噪比最大，可达0.7ηP_s/(hνΔf )。两束光不平行时，多普勒电流的大小与两束光的角度偏差关系很大；而两光束平行时，光束入射角对多普勒电流几乎没有影响。

The formula for calculating the signal-to-noise ratio is researched and showed in reference beam Laser Doppler Velocimeter. The effect of light spot size and size of light sensing surface on signal-to-noise ratio is analyzed from numerical simulation. Moreover, the formula of the Doppler current is given while the effect of the positional relation between reference beam and signal beam on Doppler current is analyzed. The theoretical analysis and simulation shows that the signal-to-noise ratio is an increasing function of light intensity of the reference beam, but when it reach a certain value, the signal-to-noise ratio increases slowly and is close to ηI_s/(hνΔf ). It can reach the maximum value 0.7ηP_s/(hνΔf ) when the Airy disk of two beams is nearly equal. The value of the Doppler current has a great correlation with the angle deviation of two beams when the two beams are non-parallel, whereas it has non-correlation with the incident angle of the beams when the two beams are parallel.