An accurate and highly sensitive label-free biosensing platform for human hemoglobin detection was demonstrated. The biosensor was derived from a micro-tapered long period fiber grating (MTLPG) functionalized by graphene oxide (GO) nanosheets. When the hemoglobin molecules are absorbed onto the fiber surface, the resonance wavelength shift, and thus the hemoglobin concentration can be detected. With hemoglobin concentration from 0.0 mg/mL to 2.0 mg/mL in deionized water, urea solution as well as glucose solution, the GO-MTLPG was implemented as a biosensor and achieved sensitivity of −2 nm/(mg/mL), −1.03 nm/(mg/mL) and −0.73 nm/(mg/mL), respectively. Moreover, the minimum limit of detection is 0.02 mg/mL, which is far below the hemoglobin threshold value of anemia that recommended by World Health Organization. In addition, the reusability of GO-MTLPG for hemoglobin detection in various interfering compounds were validated. The proposed GO-MTLPG can be developed as an optical sensor applied in biomedical and biochemical fields. © 2020 Elsevier B.V.