We propose a novel Fabry-Perot interferometer (FPI) sensor for simultaneous measurement of refractive index (RI) and temperature based on Fresnel reflection and the thermo-optic effect of silica. The sensor head consists of a short section of multimode photonic crystal fiber (MPCF) and a conventional single mode fiber (SMF), where two thin films are formed by collapsing the air holes of MPCF with a commercialized fusion splicer. Experimental results show that such a device has a linear RI sensitivity of similar to 21.52 dB/RIU (RI unit) and a linear optical path difference (OPD) temperature sensitivity of similar to 25 nm/degrees C. In addition, a high RI resolution of about similar to 1.7 x 10(-5) is obtained by using the Fourier transformation to decompose the spectral response in different spatial frequencies. Low-cost, easy fabrication and high resolution make it appropriate for practical applications. (C) 2014 Elsevier B.V. All rights reserved.