We present a combinatorial approach for development of materials for use in optical gas sensors, with oxygen being used as an exemplary target gas. Combinatorial chemistry is shown to be a promising tool for speeding up the search for new sensor materials. The method is based on the use of various polymers, solvents, indicators, plasticizers, and other additives. Solutions of the respective materials are prepared in appropriate organic solvents, and a robotic station is programmed to mix the components. Spots of the sensing materials are deposited in the wells of glass substrates resembling microtiterplates. After drying off the solvent, the sensor spots are automatically analyzed in a test stand, where they are exposed to a carrier gas containing oxygen in various concentrations. Changes in the decay time of fluorescence of the indicator probes are measured and used (along with sensor response time) as a main criterion for sensor assessment. It is shown that the combinatorial approach can reduce the time and effort needed to establish libraries of sensor materials by a factor of at least 1000. We describe in detail the device for preparation of sensor libraries and for testing the respective materials. The potential of the system is demonstrated for the characterization of optical oxygen sensors.