The structural effects, corrosion inhibition mechanisms and timeliness of 5-methyltetrazole (MT), 5-aminotetrazole (AT) and 5-mercapto-1-methyltetrazole (MMT) on copper in a 3.5 wt.% NaCl solution were studied by electrochemical experiments, surface characterizations and theoretical calculations. At the initial soaking stage, MT exhibited higher corrosion inhibition efficiency (99.65 %), which might stem from the electron donating effect and hydrophobic interaction of -CH3. While MMT exhibited lower corrosion inhibition efficiency (92.64 %), which might stem from the electron withdrawing effect and hydrophilicity of -SH. As the soaking time prolonged, the corrosion inhibition efficiencies of AT and MMT increased (99.49 % and 99.51 %). This might be because the N and S atoms of -NH2 and -SH could also provide lone pair electrons to coordinate with copper, especially S atom. As the soaking time was further prolonged, the formation of corrosion products weakened the interaction between N and S with copper, reducing the corrosion inhibition performance of AT and MMT. MT, AT and MMT molecules on Cu (111) surface can mainly undergo perpendicular adsorption, simultaneously accompanied by parallel adsorption.