Laser radar cross section (LRCS) which represents the laser scattering characteristics of a target,is applied widely in the design and evaluation of the active laser detection systems.Based on the definition of laser radar cross section,a perfect laser radar cross section model of a cat eye target with focal shift is built under the conditions of normal and oblique incidence.The computation formulas of detection distance had also been derived.The rule of LRCS and active detection distance as a function of incidence angle and focal shift had been discussed.Then the impact of incidence angle and focal shift on LRCS and active detection distance is simulated through numerical computation .The results demonstrate that the effective received area of a “cat eye” target and reflected wave divergent angle will attenuate as the incidence angle and focal shift increase which consequently result in decreasing the LRCS and active laser detection distance.The study will lay the foundation for the design and performance evaluation of various laser detection systems.