Fe3O4 nanoparticles fluid has unique optical properties, which provides versatile possibilities to design state-of-the-art photonic devices. In this paper, by combining Fe3O4 nanoparticles fluid with the photonic crystal fiber (PCF), the spectral characteristics of fluid-filled PCF under different temperatures were experimentally demonstrated. Transmission power and the long wavelength edge of the dip are both found to become highly temperature dependent. The experimental results indicate the slope of this edge is adjustable by changing temperature and there is a linear relationship between transmission power and temperature. This suggests the potential application of this device as an intensity-modulated sensing element or a tunable all-in-fiber gain equalization filter with an adjustable slope.