Abstract: A novel collimator was designed for the detector of space high energy electron,and exemplified by the one installed in China's FY-4 satellite.The original work was the addition of circular ribs inside the cylindrical shell.The trajectory of the impinging electrons through the new collimator was mathematically modeled,theoretically analyzed and numerically simulated in Monte Carlo method.The influence of collimator geometry,including the profile/number/width/spacing/depth of the individual added rib,on the anti-electron-scattering behavior was investigated for the design optimization.The simulated results show that the rib-profile and the rib-depth have the largest and the smallest impact factor,respectively.The collimator with the optimized Model-9 geometry outperforms that with the primitive Model-0 structure because of 82% reduction of the interference probability of electrons outside the field of view and because of smaller deviation from the theoretical results.