To improve the deficiencies of the current pressure-sensing structure, such as temperature crosstalk and large size, a cascaded polymer microcavity structure is prepared in the optical fiber end surface, which combined with the fiber forms an ultracompact three-beam Fabry–Pérot interferometer. Two different size interferometers are prepared to monitor the details of their interference peak changes with temperature and pressure, and the sensitivity matrix method is used to measure the ambient temperature and pressure simultaneously. The proposed sensing probe effectively avoids the crosstalk problem caused by the temperature during the pressure measurement process. In addition, the two fiber polymer probes are very compact, and the axial lengths along the fiber are only 25 and 30  μm, respectively. Therefore, the sensing probe can be applied to the sensing detection of pressure in narrow areas.