为了进一步提高主动探测系统的回波信噪比和时空分辨率，采用蒙特卡罗法建立了参与性介质中超短脉冲激光的双程瞬态辐射传输模型。基于该模型，分析了各向同性散射介质中介质物性参数和目标反射特性对高斯脉冲激光回波信号角度特性的影响。研究表明，光学厚介质中，目标回波信号的入射天顶角已达到稳定状态，峰值角度区间为30°~40°，能量集中范围为30°~50°，且其时间展宽特性与所处角度区间无关；光谱衰减系数对回波信号的能量衰减和脉冲宽度均存在强烈影响，散射反照率则着重体现在后期回波信号的能量衰减上；镜反射引起的高强度前期回波信号减弱，镜-漫反射间目标回波信号的绝对差值极其微小，呈现弱关联性。可为选通摄像机的设计选型及脉冲激光器的波长选取提供参考借鉴。

To improve the echo signal-to-noise ratio and temporal-spatial resolution of active detection systems further, the two- way transient radiative transfer model of ultrashort pulse laser in participating medium is established using Monte Carlo method. Based on the model above, the influence of medium properties and target reflective characteristic on the angular characteristic of Gaussian pulse laser echo signal in isotropic scattering medium is analyzed. Research shows that the incident zenith angles of target echo signal have reached its steady state in optically thick medium, with the peak angle interval of 30°~40° and the energy concentration range of 30°~50° , but the temporal broadening characteristic is irrelevant to angle intervals; the spectral attenuation coefficient affects the energy attenuation and pulse width of echo signal strongly, but the scattering albedo embodies in the energy attenuation of post-echo signal mainly; high intensity pre-echo signal caused by specular reflection weakens, and the absolute difference of target echo signal is extremely small between specular reflection and diffuse reflection, with weaker relevance. The reference for gated-camera design selection and pulsed laser wavelength is provided.