Abstract: Interfacial effect on effective optical properties of a granular composite has been investigated, in which spherical particles with graded interfaces are randomly embedded in a host matrix. Under the dilute limit, the effective dielectric coefficient of the composite is derived by means of the first-principle approach method applied to power-law dielectric gradation profile in interfaces. The effective optical responses of graded and sharp interfaces are discussed, respectively. It is found that the graded interface in graded spherical particles yields a broader optical absorption spectrum with blue-shift and the fluctuation of corresponding effective dielectric response is smaller.