To separate two polarized lights with wavelengths at 810 nm and 850 nm, respectively, into two optical beams while keeping their polarization directions unchanged and degree of polarization maximized, a dichroic beam-splitter at incidence angle of 45°was designed and fabricated. The 810nm beam passes through the splitter while 850nm beam is reflected. An apposite initial film configuration was selected to control the separation of s- and p-polarization components. It was further optimized with the Global Modified LM method in Film Wizard software. The phase and energy parameters of the seperated two beams meet the design target. TiO2 and SiO2 have been chosen as high- and low-refractive index layer materials, respectively. Ion beam-assisted deposition, optical extreme value method, and quartz crystal oscillator have been used to control the thickness of films. The extinction ratio of obtained sample reaches 7000 ∶1 in 810 nm beam and 20000 ∶1 in 850 nm beam. The control of phase and energy of optical thin films were realized to meet the demands of polarization state coding for its application in communication.