A real-time radon monitoring system which can simultaneously measure radon concentrations in multiple sites was developed and tested. The system consists of maximum of four radon detectors, optical fiber cables and a data acquisition personal computer. The radon detector uses a plastic scintillation counter which collects radon daughters in the chamber electrostatically. The applied voltage on the photocathode for the photomultiplier tube(PMT) acts as an electrode for radon daughters. The thickness of the plastic scintillator was thin, 50um, so as to minimize the background counts due to the environmental gamma rays or beta particles. The energy discriminated signals from the radon detectors are fed to the data acquisition personal computer via optical fiber cables. The system made it possible to measure the radon concentrations in multiple sites simultaneously.