Optical performance monitoring (OPM) is one of the key techniques of the reconfigurable wavelength-division-multiplexing (WDM) optical networks. When the optical communication speed rises from 10 to 40 Gb/s and above, the residual chromatic dispersion (CD) tolerance of the optical channel is only 1/16 of the former 10 Gb/s system. So CD monitoring is the critical technique for WDM optical channels. Integration and all-optical domain can be achieved when using the nonlinear effects of optical waveguides to realize CD monitoring. Silicon optical waveguides have the relatively large nonlinearity with the nonlinear refractive index as 5×10-18 m2/W. After going through the WDM network with CD effects, the signal light wave has the four wave mixing (FWM) effect with the probe light in the silicon waveguide. This FWM effect induces changes in the output spectrum, and different dispersions of the optical channel lead to the varied effects of FWM. So, when detecting the different spectrum changes relates to FWM, the optical channel CD can be monitored. In this paper a 3 cm silicon optical waveguide is adopted with the loss index of 0.2 dB/cm. The monitoring dispersion range can be ±40 ps/nm. The results indicate that this OPM technique can be used to monitor the CD of the optical network on chip level.