H9N2 subtype avian influenza virus (AIV) is a low-pathogenicity AIV that seriously threatens the healthy development of the poultry industry and public health systems. By developing rapid, sensitive, and accurate methods suitable for field detection of H9N2 AIV, we could efficiently control the viral infection and its spread over time. This study proposes a novel biosensor with high specificity and a low limit of detection (LOD) for H9N2 AIV detection. The sensor employs a dual-resonance long-period fiber grating (DR-LPFG) modified with TiO₂ nanoparticles (nano-TiO₂). Anti-H9N2 monoclonal antibody molecules (anti-H9N2 MAbs) are covalently bound to the TiO₂ surface carboxyl groups on the surface of the DR-LPFG, thus preparing the biosensor. The biosensor measures the variation of the dual-resonance wavelength spacing (Δλ) caused by the specific interaction between the fixed anti-H9N2 MAbs on the surface of DR-LPFG and H9N2 AIV antigen. In experimental tests, the Δλ sensitivity of the nano-TiO₂ coated DR-LPFG sensor is about 1063.44 nm/RIU (where RIU is the refractive index unit) in the refractive index range 1.3320--1.3760. The LOD of the proposed biosensor for H9N2 AIV is ~2.7 ng/mL, 96.1% greater than that of a DR-LPFG-based biosensor modified with Eudragit L100 copolymer. The biosensor saturates at 50 μg/mL, and its affinity coefficient to H9N2 AIV is ~3.57×10 ⁸ mol ^-1·L. The biosensor also shows a high specificity and a rapid detection for H9N2 AIV, affirming its high application potential in biomedical fields such as clinical diagnosis and drug analysis.