In this study, a new type of multifunctional sensor is designed, applied for monitoring the temperature, refractive index (RI) or gas pressure. The proposed sensor is composed of a waveguide and a multiple-resonant cavity in two-dimensional photonic crystal with hexagonal lattice. And characteristics simulation analysis has been demonstrated by finite difference time domain (FDTD) method. The results of the numerical analysis show that the RI sensitivity is about 1000 nm/ RIU with the range from 1.0 to 1.03 RIU and the temperature sensitivity is 35 pm/°C. In addition, according to the linear dependence between the RI and gas pressure, the proposed sensor can also be applied to gas pressure measurement. Using the difference between the sensitivities of different resonances, the mutual interference between the different measurements can be eliminated. The proposed multifunctional sensor has distinct advantages, such as simultaneous multiple signal sensing ability, high sensitivity, small size, and linear response, which make the device attractive to the applications of physical, chemical and biological sensing technology.