In the study, a novel compound of dodecyliminodimethylenediphosphoinc acid was synthesized, and its adsorption mechanism onto ilmenite surface was investigated by zeta potential, Fourier transform infrared (FTIR) and X-ray photoelectron spectroscop (XPS) measurements. The zeta potential measurement results indicated that dodecyliminodimethylenediphosphoinc acid (DDDA) could adsorb onto ilmenite surface, and the optimum pH range for adsorption was 4-8 (similar to the flotation behavior). The FTIR analyses further confirmed that DDDA chemisorbed onto ilmenite surface and formed metal-DDDA complex, rendering the hydrophobic media for flotation. The XPS results provided strong evidences that DDDA species chemisorbed onto ilmenite surface and reacted with Fe ions rather than Ti ions.