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This study developed an inexpensive and simple microsensor for detecting volatile organic compounds (VOCs). In general, solid state based VOC sensors which use metal oxide as the sensing materials have to work at a temperature of about 300 - 350°C. Alternatively, this research developed a VOC sensor capable of sensing VOCs at room temperature, resulting in a sensor system of low energy consumption. This developed VOC sensor is composed of a nano-porous polyimide (PI) film doped with carbon black (CB) as the sensing material. The conductivity of the PI/CB film changed after absorbing VOC contents in the air. A post pore opening procedure by plasma etching is used to enhance the response of the sensor film. SEM images confirm that the micro-pores interconnect with their neighboring pores and also open to the outside air. Results indicate that the developed VOC sensor has a good repeatability for detecting VOCs. PI film with 1% (weight percent) of CB has the best sensitivity due to the well dispersion of CB. The film prepared with pore opening procedure exhibit a response of 5 times faster than the film prepared without pore opening. The sensor developed in this study provides a simple and straight forward method to fabricate low-cost VOC sensors.