A simultaneous optical isolation and channel monitoring system for monitoring a channel of an incident light is provided. The system includes an optical isolator for receiving an incident light so as to isolate an interference of backward light into the cavity of laser source or an optical amplifier, wherein after passing through the optical isolator, the incident light has a different polarization state output changing with a wavelength thereof, a beam splitter connected to the optical isolator for separating the light into a light to output and a light for monitoring signal, a linear polarizer connected to the beam splitter for filtering a quantity of signal from the monitored light, and a photodetector connected to the linear polarizer for detecting the quantity of signal generated from the monitored light so as to monitor the channel.