We developed a variable-temperature scanning microwave microscope (VT-SμM) that can perform high-throughput materials characterization in the temperature range between 4K and room temperature. As a sensor probe we used a high-Q coaxial cavity resonator, which was mounted on the low-temperature stage to allow variable-temperature measurements. We carried out systematic studies on the thermal degradation of the conducting polymers using the combinatorial libraries of polyaniline and polythiophene thin films, which showed rapid decrease of conductivity above the heating temperatures of 300°C and 250°C, respectively. The low-temperature performance of the VT-SμM was demonstrated by the measurement of composition-spread Nd1-xSr xMnO3 thin film, for which we succeeded in detecting the clear metal-insulator transition at 100K. We also propose a simple and easy method for the quantitative analysis of conductive thin films, by using the standard composition-spread thin films of Ti1-xNbxO 2.