The work aims to study synergetic effect of KI and thiourea on corrosion inhibition of disodium lauroamphodiacetate. Corrosion inhibition of corrosion inhibitors including triethanolamine, EDTMPS and disodium lauroamphodiacetate (M) was tested in static weight-loss method, respectively. Disodium lauroamphodiacetate which exhibited the optimal corrosion inhibition effect was selected as main ingredient of compound corrosion inhibitor. Then complex synergism experiment was performed to the disodium lauroamphodiacetate. Surface morphology of corroded steel slabs (Q235) was observed with a 3D laser confocal microscope, and corrosion product film on the steel slabs was characterized with SEM and X-ray energy dispersive spectrum (EDS). Inhibition rate increased by 7%, corrosion rate decreased by 0.0105 mm/a and corrosion inhibition effect was the best at the KI:M ratio of 1:5 (M5K). Inhibition rate increased by 5.8%, corrosion rate decreased by 0.0114 mm/a and corrosion inhibition effect was slightly inferior to that of M5K at the KI:M ratio of 1:10 (M10S). KI or thiourea have an excellent synergetic effect on corrosion inhibition of disodium lauroamphodiacetate at specific KI:M ratio. KI enhances its adsorption performance while thiourea has sequestration effect, which provides certain reference for the studying synergetic effect on corrosion inhibition of amphoteric imidazolines.