A novel optical fiber Fabry-Pérot (F-P) refractive-index sensor is reported. A micro-hole is made by etching the tip of a cleaved erbium-doped fiber (EDF). We fabricate a self-enclosed F-P cavity inside an optical fiber by splicing the first fiber to another cleaved fiber. The micro-hole by etching is a flute,a microchannel is made by cleaving and then polishing near the flute,and the light could return which results in F-P interferometer unharmed. The liquid could easily get into the F-P cavity by capillarity. According to the F-P interference principle,the reflection spectra pit wavelength of the sensor is linear with refractive index in the cavity. The experimental results show that the linearity is 0.9996 and the sensitivity is 1068 nm/RIU at the refractive-index range of 1.3333 to 1.3899. The sensor is all-fiber structure,having many advantages such as small size,steady structure,high precision,enduring cautery,etc. It could meet subminiature applications for refractive-index measurement.