The inhibition effect of tinidozole on the corrosion of mild steel in 3% HCl solution has been investigated through weight loss measurements, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and quantum chemical calculations methods. The results show that tinidazole is an effective inhibitor for mild steel corrosion in HCl solution, and that the inhibition efficiency reaches a maximum value of 62% at the concentration of 400mg/L. Polarization measurement suggests that the tinidozole acts as mixed-type inhibitor. The Langmuir adsorption isotherm is proposed to interpret the interaction for the inhibitor molecule on metal surface. Furthermore, the quantum chemical calculation reveals that the adsorption of tinidozole is mainly concentrated around the imidazole ring.