A method for detecting protein molecules based on the tilted fiber Bragg grating (TFBG) surface plasma resonance (SPR) is proposed to achieve the quick online real-time detection of trace amount of proteins. The detection principles of the TFBG-SPR protein molecular probe are analyzed, and its feasibility is demonstrated. The intermediary material between the protein molecules and the golden layer outside of the fiber gratings is cysteamine hydrochloride. When the concentration of the cysteamine hydrochloride solution is 2 M, the shift of the TFBG resonance peak is 2.23 nm, illustrating that the cysteamine hydrochloride modifies the gold film successfully. IgG antigen solution is poured on the surface of the cysteamine hydrochloride modifying the gold-deposited TFBG. Finally, antigen-antibody hybridization experiment is carried out with a 10 mg/mL antibody solution, and after two hours of hybridization the resonance peak of the TFBG shifts 5.1 nm, which validates the feasibility and effectiveness of the TFBG-SPR protein molecular probe.