为了改进分光计测量三棱镜顶角实验中涉及的复杂位姿调节和操作步骤，优化装置结构空间，提升测量效率，本文提出一种双镜反射法. 该方法以激光作为光源垂直入射三棱镜底面并在棱镜斜面上折射，折射光在调至平行的两反射镜间多次反射后被CCD探测器靶面接收形成一个激光光斑，记录光斑的中心位置S1；将三棱镜旋转一个已知的小角度β，此时光斑发生位移，记录位移后的光斑中心位置S2，计算出S1与S2的位移量ΔS. 最后通过角度β、位移量ΔS和测量公式计算三棱镜顶角a的大小. 实验结果表明，当两反射镜间隔为65 mm~95 mm之间，旋转角度β选择在0.1°～0.2°时，待测三棱镜顶角a的测量值与标准值之间的测量误差不超过0.25%. 该方法不涉及分光计中复杂的望远镜调节，采用两反射镜和CCD相机自动读数程序界面，不但能够折叠系统光路、减少仪器重量和优化装置空间，且具有较高的重复测量精度.

 In order to improve the complicated pose adjustment and operation steps involved in the experiment of measuring the top angle of the prism by spectrometer，optimize the structure space of the device and improve the measurement efficiency，a double-mirror reflection method is proposed. In this method，the laser as the light source is vertically incident on the bottom surface of the prism and refracted on the slope of the prism. The refracted light is reflected several times between the two parallel mirrors and received by the target surface of the CCD detector to form a laser spot，and the center position of the spot S1 is recorded. Rotate the prism by a known small angle β，at which time the light spot shifts，record the center position of the light spot after the shift S2，and calculate the displacement ΔS between S1 and S2. Finally，the angle β，the displacement ΔS and the measurement formula are used to calculate the top Angle a. The experimental results show that when the interval of two mirrors is between 65 mm and 95 mm，and the rotation Angle β is selected between 0.1° and 0.2°，the measurement error between the measured top Angle a of the prism to be measured and the standard value is less than 0.25%. This method doesnt involve complex telescope adjustment in the spectrometer. It not only folds the system optical path，reduces instrument weight，and optimizes device space，but also has high repeated measurement accuracy by using the double mirrors and an automatic reading program interface with a CCD camera.