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.