To reduce the corrosion of Q235 steel, environment-friendly and efficient N-doped carbon dots (N-CDs) were synthesized using 4-amino salicylic acid (4-ASA) and l-histidine (l-His) as precursors. The corrosion inhibition behavior of N-CDs for Q235 steel in 1 M HCl solution was systematically investigated using a weight-loss experiment, an electrochemical test, and corrosion morphology. Results showed that N-CDs could effectively inhibit the corrosion of Q235 steel, and the inhibitory efficiency reached 93% at 50 mg L-1. Quantum chemistry and molecular dynamics were used to study the inhibition mechanism of N-CDs. The results demonstrated that N-CDs exhibited a strong adsorption force on metal and the adsorption process followed the Langmuir adsorption isotherm, indicating physical/chemical mixed adsorption.