A polymer micro-cavity based probe-type fiber Fabry-Perot interferometer is demonstrated by coating PDMS at the end tip of the single mode fiber, at the same time, the refractive index (RI) and temperature sensing characteristics of the sensor are also investigated. The refractive index and temperature sensing are based on extinction ratio measurement and wavelength shift measurement, respectively. Meanwhile, the theoretical analysis of the special refractive index sensing characteristics of the sensor is conducted, which can be used to design sensors. The sensor has a simultaneously high sensitivity to refractive index and temperature, the refractive index sensitivity is -180.359 dB/RIU (RI unit) in the refractive index range of 1.3625～1.4206, and the temperature sensitivity is 355.28 pm/℃ in the temperature range of 25 ℃～60 ℃. The sensor has the merits of compact size and good biocompatibility. It is advantageous in applications for biochemical activity detection when compared to the conventional fiber sensors, such as tissue culture.