There is temperature and pressure cross-sensitivity when using ordinary fiber to detect pressure. In order to solve this problem, a fiber Bragg grating pressure and temperature sensor based on double equal thickness and equal strength cantilever beam was proposed in this paper. Feasibility of the structure was verified by theoretical analysis and simulation. The first sensing element of the sensor is a cantilever beam with equal thickness and strength. It mainly consists of temperature-strain sensitization zone of bimetal and load-bearing zone of stress-strain optical fiber. The second sensing element consists of two fiber Bragg gratings with different grating spacing distributed on a single fiber along the axial direction. The distance between these two gratings are predetermined. Because the initial grating spacing of the two fiber Bragg gratings is different, the corresponding demodulated wavelength varies and possesses a certain wavelength difference as well. Hence, the measurement of two different parameters can be realized. The first Bragg grating is fixed on the bimetal temperature sensing region and cannot measure pressure as it does not vary with external pressure. The theoretical derivation of optical fiber sensing proves that the distance between the two peaks (the wavelength difference between the two peaks) of the second Bragg grating reflectance spectrum is only proportional to the pressure and independent of temperature variation. From this principle, the pressure is measured. The simulation results reveal that the proposed structure can realize two-parameter measurement of pressure and temperature. The fiber Bragg grating detection device has the advantages of low cost, stable and reliable operation.