In order to promote the rapid development of green plant extract as corrosion inhibitors, orange peel extract (NOPE) was used as corrosion inhibitor to Q235 steel in phosphoric acid environment. Orange peel extract (NOPE) was obtained by simple reflux extraction using anhydrous ethanol and acetone. The main groups of orange peel extract (NOPE) and stability of main ingredients in phosphoric acid were confirmed by an infrared spectroscopy (FTIR) and an ultraviolet spectroscopy (UV). The corrosion inhibition performance of orange peel extract (NOPE) to Q235 steel in 0.5 mol/L H3PO4 solution was investigated by weight loss, dynamic potential polarization (PDP), linear polarization (LPR) and electrochemical impedance spectroscopy (EIS). The influence of temperature on thermodynamic parameters (Ea,ΔHaΘ and ΔSaΘ) and adsorption properties (ΔGΘads, ΔHΘads and ΔSΘads) was studied by calculation. The corrosion rate of Q235 steel was significantly slowed down in 0.5 mol/L H3PO4 medium system with orange peel extract (NOPE) and NOPE belonged to the mixed corrosion inhibitor mainly to inhibit the dissolution of anode metal. With the concentration increase of orange peel extract (NOPE), the anode current was reduced and the active corrosion site was blocked, the corrosion rate was reduced and the inhibition efficiency was increased. The corrosion inhibition efficiency of Q235 steel was above 90% at the temperature of 303 K and the concentration of 3.0 g/L orange peel extract (NOPE) using different test methods such as weight loss, PDP, LPR and EIS. The corrosion inhibition efficiency of Q235 steel was reduced with the increase of system temperature. The thermodynamic activation parameter (activation energy) Ea of the system with orange peel extract (NOPE) was significantly increased compared with the blank system, and the difference of (Ea－ΔHaΘ) was equal to the mean value of RT (2.64 kJ/mol) at per concentration, so it could be inferred that the corrosion process was a monomolecar reaction. Moreover, the adsorption of the active component of orange peel extract (NOPE) on the surface of Q235 steel was in accordance with Langmuir isotherm and physical adsorption was dominant, which further proved that the adsorption was monolayer adsorption. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and contact angle measurement all proved the existence of corrosion inhibition on the steel surface and reduced the acid corrosion rate of Q235 steel. Quantum chemical studies confirmed that the better corrosion inhibition and adsorption performance of NOPE on Q235 steel was due to the functional groups of hesperidin and flavone. The orange peel extract (NOPE) has good corrosion inhibition performance to Q235 steel in the 0.5 mol/L H3PO4 solution system. It is a green corrosion inhibitor with good application prospect in the pickling field, and can provide certain guidance for the development of plant extract corrosion inhibitor.