为了实现任意球面元件的超高反射率测量，提出直腔和折叠腔两种光腔结构，以实现0°,10°,15°和30°等不同角度下球面元件的超高反射率测量。详细分析了这两种测量方式，根据光束传输变换公式，推导了任意球面元件在测量中引入的衰荡光腔物理腔长的变化，得到了实验测量中腔长调节指导。并根据光腔衰荡法原理，推导了球面元件在超高反射率测量中的通用数学表达式，对测量公式进行了讨论，分析结果扩展了光腔衰荡法在元件超高反射率测量的使用范围。

In order to measure superhigh reflectivity of any sphere optical element at different angles, such as 0°, 10°, 15°, 30° and so on, two optical resonator structures are put forward: one is straightcavity, and the other is foldedcavity. Physical length of the ringdown cavity is defined based on the concept of light path. These two kinds of measurement methods are analyzed in detail. When spherical surface is put in the ringdown cavity, it brings length misalignment of the ringdown cavity. This varied length is derived based on the beam transmission and transformation law, which can be used as length adjustment guidance of the ringdown cavity for reflectivity measurement. In addition, according to reflectivity measuring principle of cavity ringdown, mathematical expressions of reflectivity measuring for spherical components are deduced at different angles, which are discussed separately. The results expand the superhigh reflectivity measurement scope of optical elements for the cavity ringdown method.