分析了聚焦光束在介质中的传播情况，利用VC++语言编制了一套平圆光束聚焦在半无限大生物组织内传播的Monte Carlo模拟程序，对几种不同参数值的情况进行了模拟，通过对模拟结果的分析，得出了平圆光束聚焦在半无限大生物组织内传播的规律。

The focused beam propagation in turbid medium is analyzed. A Monte Carlo simulation model for simulating the focused flat circular beam propagation in a semi-infinite bio-tissue is constructed. Using this model, we study the absorbed photon density with different tissue parameters in the case of a focused flat circular beam injecting the tissue. The simulation results show the law of optical propagation in the tissue.