Star-forming viscous disk model was proposed by Lin & Pringle (1987) as an ubiquitous mechanism to form the exponential stellar disk of spiral galaxies. To clarify whether the viscous evolution models can explain the chemical properties of general spiral galaxies, we have studied the chemical evolution of star-forming viscous disks under the several physical conditions in relation to the possible processes of the disk formation, and compared with the observed gas and metallicity distributions of spiral galaxy disks.