The nonlinear optical properties of a soluble and π electron conjugated organic polymer: poly (2,5-dialkoxyphenylene) (abbreviation called PPP) were studied by degenerate four-wave mixing (DFWM) at 532 nm and 1064 nm. The third-order nonlinear optical coefficient and nonlinear refractive were measured, and the figure of merit is discussed to point out the suuitable wavelength for PPP practical application.