Coaxial cable Fabry-Perot interferometer has been reported as a temperature sensor by drill two holes on a coaxial cable. For high temperature applications, traditional flexible cable will not deliver any signal due to the low melting point of the dielectrics. Ceramic coaxial cable can withstand high temperature, but drilling holes is not good enough to create reflectors for use in a interferometer. In this paper, we propose a method of filling the drilled holes with conductive materials to increase the reflection. The influences of the hole drilling and the material filling are studied. The resulted sensor is then tested in a furnace. The sensor can withstand as high as 650 degree celcius before abnormal behavior. The temperature response below 300 degree celcius is relatively flat, maybe due to the conflicting properties of the material when temperature rising. It is also possible that the flat behavior under 300C can be utilized as a temperature insensitive device to measure stress or other parameters.