In this paper a fluid sensor has been proposed based on two dimensional photonic crystal cavity. The cavity is a L7 cavity with W1 waveguide below the cavity for coupling light into the cavity. A dip in the output transmittance has been observed and the quality factor of the dip is found to be ~629. Further, to improve the performance of the cavity another L7 has been introduced below the W1 waveguide. The quality factor of the proposed structure is found to be ~3413. The proposed PCC structure has been used as a fluid sensor for the sensing of kerosene, heptane, cotton seed oil, methanol, cresol and acetic acid. The proposed structure has high quality factor and will be easy for fabrication and hence can be used as an ideal fluid sensor.