In this study, we used an e-beam evaporation method to deposit SiO2 and Ta2O5 single-layer films on glass substrates, then the extinction coefficients (k values) and refractive indices (n values) of the deposited films were measured using a thin-film analyzer in the range of 300–1000 nm. The k values of the SiO2 and Ta2O5 single-layer films were almost zero in the measured range and the n values decreased slightly with increasing light wavelength. The measured n values of the SiO2 and Ta2O5 single-layer films were used to design a green-wavelength distributed Bragg reflector (DBR) with a central wavelength of 550 nm. The thicknesses (d) of the SiO2 and Ta2O5 single-layer films for the quarter wavelength (λ/4) for green light (550 nm) were calculated using d = λ/(4n) to be 94.17 and 64.55 nm, respectively. Next, the measured n values and the calculated thicknesses of the SiO2 and Ta2O5 single-layer films were incorporated into the overall transfer matrix (OTM) investigated by ourselves, and COMSOL Multiphysics® software was used to calculate and simulate the reflectance spectra of the designed green-light DBR with two, four, and six periods. Sheppard’s approximate equation was also used to calculate the maximum reflectance ratios of the designed green-light DBR, and the calculated values were compared with those obtained by OTM and COMSOL simulations. We discuss the reasons for the differences between these calculated results.