本研究的目的在于获得Nd∶YAG激光在血液中传播的几何尺寸损耗与血液厚度的关系，从而获得适用于Nd∶YAG激光在血液中传播的修正朗伯比尔定律的准确表达式。通过所建立的Nd∶YAG激光在离体血液中透过的光检测实验系统，检测得到激光在穿透目标厚度为1.0~2.5 mm（临床脉管性病变的常见血层厚度）的圆柱形血层后的光衰减情况，并基于R语言和统计学方法，建立了几何尺寸损耗与血液厚度之间的线性、对数、指数和乘幂回归模型。其中，线性回归模型的拟合效果最好，R²值可达0.9219，由此获得适用于Nd∶YAG激光在血液中传播的修正朗伯比尔定律表达式。

To acquire the exact expression of the modified Beer-Lambert law for the transmission of Nd∶YAG laser in blood, the relationship between a geometry-dependent factor and blood depth must be clarified. In this study, we built a laser energy detecting system that can measure the transmitted Nd∶YAG laser energy using in vitro blood samples. Laser decay was measured in cylinder-shaped blood layer with a thickness of 1.0-2.5 mm, which is the typical blood layer thickness in clinical vascular diseases. Statistical methods and the R language were used to build linear, log, index, and power regression models of the geometry-dependent factor with blood thickness as an independent variable. The highest R² value among these four models is 0.9219, corresponding to the linear regression model. Based on the abovementioned results, the exact expression of the specially modified Beer-Lambert law has been built for Nd∶YAG laser transmission in blood.