Various highly effective shielding composites with low cost, light weight, and easy processing were fabricated by addition of various amounts of BaZrO3 and Ba2P2O7 to unsaturated polyester resin. The composites were analyzed by Fourier transform IR spectroscopy, scanning electron microscopy, energy-dispersive X-ray analysis, and X-ray diffraction. A high-purity germanium detector-based gamma spectrometer for experimental tests, WinXCom for theoretical calculations, and Geant4 for simulations were used to analyze the high-energy ionizing radiation shielding performances. The shielding results showed that there is good consistency (relative deviations less than 10%) among the three techniques. Addition of BaZrO3 and Ba2P2O7 as a filler in the composite enhances the radiation protection characteristics of the unsaturated polyester, and the composites with 20% BaZrO3 and 20% Ba2P2O7 had the most effective radiation shielding performance. Consequently, these innovative composites as radiation shielding materials are predicted to benefit medical physics and nuclear science applications.