Abstract. The extinction generally occurs whenever electromagnetic radiation propagates through a medium containing small particles. The spectral dependence of extinction or extinction curve is a function of composition, structure and size of the particles. In the present work, we study the extinction efficiency (Qext) of interstellar dust in the wavelength range 0.11 to 3.4 μm. We propose a model which considers interstellar dust as a mixture of compact and aggregate particles, with composition of silicate and graphite. We consider compact particles as spheroidal particles and aggregates as Ballistic Cluster-Cluster Aggregate (BCCA) with some size distribution within a size range 0.004 to 0.31 μm. We then generate the normalized average extinction curves in the wavelength range 0.11 to 3.4 μm. It is found from our work that the proposed model can successfully reproduce the observed interstellar extinction curve. The extinction generally occurs whenever electromagnetic radiation propagates through a medium containing small particles. The spectral dependence of extinction or extinction curve is a function of composition, structure and size of the particles. In the present work, we study the extinction efficiency (Qext) of interstellar dust in the wavelength range 0.11 to 3.4 μm. We propose a model which considers interstellar dust as a mixture of compact and aggregate particles, with composition of silicate and graphite. We consider compact particles as spheroidal particles and aggregates as Ballistic Cluster-Cluster Aggregate (BCCA) with some size distribution within a size range 0.004 to 0.31 μm. We then generate the normalized average extinction curves in the wavelength range 0.11 to 3.4 μm. It is found from our work that the proposed model can successfully reproduce the observed interstellar extinction curve.