To meet the requirements for the safety of the space environment and the increasing demand for the detection of faint targets in deep space, using a space-based detection optical system with a wide field of view (FOV) has become a major trend. However, such systems are very susceptible to stray light. Based on the above background, we design a baffle with angled and parallel vanes under the limitation of a miniaturized baffle, and we propose a vane angle optimization method. The method is proposed by establishing an irradiance transfer model based on the bidirectional scattering distribution function with Gaussian statistics on the surface of baffle and vane. In addition, the result of the point source transmittance (PST) obtained by Monte Carlo simulation in LightTools indicated that the PST is improved by 2 to 5 times in the FOV of 30 deg and 70 deg when the angle of incidence is at the stray light exclusive angle compared to the traditional method. Meanwhile, the method establishes an analytical expression; therefore, the optimization process is more efficient, and the time required for simulation can be significantly reduced.