Butadiene-acrylonitrile-butylacrylate rubber (BNBR), which is synthesized by copolymerization of butadiene, acrylonitrile, and butyl acrylate, retains excellent properties of oil resistance and heat resistance because of the introduction of -CN, -COOR in the polymer. However, the presence of a lot of carbon-carbon double bonds (-C=C-) could lead to deterioration of material properties such as thermal stability and ozone resistance. To improve the properties of unsaturated elastomers, further chemical modification of diene-based polymers is very critical. Hydrogenation is a useful chemical modification method that can improve the thermal stability of diene-based polymer. BNBR was hydrogenated by homogenous hydrogenation using the Wilkinson catalyst RhCl(PPh3)3 in xylene. The effects of catalyst concentrations, reaction times, and hydrogen pressures on the conversion and product selectivity were discussed. The degree of hydrogenation was measured by proton nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy. The thermal stability of hydrogenated and nonhydrogenated copolymers was evaluated by thermogravimetric analysis (TGA). The CCD camera was used to characterize the ozone resistance of hydrogenated copolymer (HBNBR). The results obtained by TGA and the CCD camera show that the maximum saturation level is a critical factor for improvement of thermal stability and the ozone resistance of HBNBR.