A high-sensitivity temperature sensor based on dual-core fiber coupling effect and vernier effect was proposed. The sensor was composed of two fibers which with a certain length difference, they were dual-core photonic crystal fiber and single mode fiber. The vernier effect was achieved by dual-core photonic crystal fiber through the cascade, and in the meantime the temperature sensing was achieved by filling the pores with ethanol in the middle of the fiber core. The simulation results show that the average temperature sensitivity of -20.37 nm/℃ of the temperature sensor can be achieved in the temperature range of 35℃~45℃. Compared with the sensor which only depends on the energy coupling effect of dual-core photonic crystal fiber, the temperature detection sensitivity of the proposed sensor is 10 times higher.