Substrate processing system, method of managing the same and method of manufacturing semiconductor device with the same

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.