Microstructured fibers with geometric versatility, and exceptional guiding properties, show unique advantage in constructing high-performance sensors. In this paper, a sensitivity-enhanced fiber-optic sensor based on an exposedcore single-hole microstructured fiber (SHMF) is proposed and experimentally demonstrated for the refractive index (RI) measurement of liquid samples. Experimental results show that the RI sensitivity of the exposed-core microstructured fiber is 375.77 nm/RIU in the low-range of 1.3409~1.3522. With the advantages of enhanced lightmatter interaction ability, tight light confinement and mechanical robustness, the proposed sensor based on exposedcore single-hole microstructured fiber offers great potential in biological and chemical sensing applications.