The present study assessed the catalytic performance in epoxidation of styrene using tert-butyl hydroperoxide (TBHP) as an oxidant over single-atomic copper-doped Ordered mesoporous alumina (Cu-OMA) composited with g-C3N4 (CN). The thermal treatment at three temperatures (300, 500, 700°C) provided a facile mean to modify the texture and electronic structure of the Cu-OMA@CN composite. The X-Ray absorption spectroscopy proved the single-atomic Cu-O-Al and Cu-O-C in Cu-OMA@CN-500 catalyst. Catalytic reaction parameters, namely temperature (60-80°C), catalyst amount (10-70 mg), substrate/oxidant ratio (1:1-1:3), and solvents (acetone, ethanol, acetonitrile, N, N-dimethylacetamide) were optimized to obtain high conversion of styrene and selectivity to styrene epoxide. Under the optimized reaction conditions (75°C, 30 mg of catalyst, 1:2 of styrene/TBHP and acetonitrile as solvent), the conversion decreased in the order of Cu-OMA@CN-500 > Cu-OMA@CN-300 > Cu-OMA@CN-700. This sequence was related to the formation of electron-rich single-atom copper sites, high surface area, medium alkaline environment of Al2O3 and high content of graphic nitrogen species. The most active Cu-OMA@CN-500 catalyst displayed a high styrene conversion (87.2%) and striking selectivity to styrene oxide (90.0%). Its catalytic activity was retained after five recyclability tests. The possible catalytic mechanism for epoxidation of styrene over Cu-OMA@CN-500 was tentatively proposed.