A label-free glucose biosensor was developed using a long period fiber grating (LPFG) functionalized with graphene oxide (GO) and glucose oxidase (GOD) via a chemical crosslinking method. The GO-coated LPFG provided abundant binding sites for the immobilization of GOD due to its high surface-to-volume ratio. The reaction between GOD and glucose generated gluconic acid and H2O2, which caused a noticeable shift in the LPFG transmission spectrum due to the change in the surrounding refractive index. The biosensor exhibited a linear response with a response coefficient of 0.77 nm/(mg/mL) and good selectivity, making it suitable for practical applications. The optimal conditions for the biosensor were determined, including a GOD concentration of 4 mg/mL and a pH of 7. The biosensor demonstrated excellent linear response in the low concentration range of 0-1.2 mg/mL with a sensitivity of ∼0.77 nm/(mg/mL), fast response speed, and short response time (2.16 s). The GOD-GO-modified LPFG biosensor has great potential for use in the fields of pharmaceutical research and medical diagnosis.