Using first-principle calculations, we compare the catalytic activity of the experimentally available C- or Si-doped boron nitride nanosheet (C-/Si-BNNS) towards the epoxidation of ethylene by N2O molecule. The epoxidation reaction of ethylene over these surfaces includes the decomposing of N2O into N2 and an oxygen atom (Oads), formation of the ethyleneoxy intermediate, and the creation of ethylene oxide. Our results show that the catalytic activity of C-BNNS for epoxidation of ethylene is better than Si-BNNS, due to more favorable charge-transfer effects. The results presented here suggest a green, low-cost, and metal-free approach for low-temperature epoxidation of ethylene using C-BNNS.