In this work, we use spectroscopic ellipsometry (SE) to study the optical properties of InAsn/AlAsn short-period superlattices (SPS) with different period thicknesses for a wide wavelength range of 250 nm − 1650 nm (about 0.75 eV – 5 eV). Additionally, the InAs2/AlAs2 samples grown at various temperatures (450, 475, 500, 525, 550 ℃) were investigated. We extract the dielectric functions and adapt Adachi's model to obtain the interband transition energies of E0, E0+Δ0, E1, E1+Δ1 and E2. The quantum confinement effect and the strain effect lead to the decrease of E0, E0+Δ0, E1, E1+Δ1 with the increase of period thickness. It is also found that as the growth temperature rises from 450 ℃, all the transition energies decrease as a result of the increase in the amplitude of lateral composition modulation and the relaxation of the compressive strain in InAs layers.