Provided are substrate processing systems and methods of managing the same. The method may include displaying a notification for a preventive maintenance operation on a chamber, performing a maintenance operation on the chamber, performing a first optical test, and evaluating the preventive maintenance operation. The first optical test may include generating a reference plasma reaction, measuring a variation of intensity by wavelength for plasma light emitted from the reference plasma reaction, and calculating an electron density and an electron temperature from a ratio in intensity of the plasma light.