Based on an excitonic basis, the intraband dynamical process and optical absorption spectrum of semiconductor superlattice in terahertz fields are investigated with the density matrix theory. The excitonic Bloch oscillation is driven by the terahertz field. The slow variation in the intraband polarization depends on the terahertz frequency. With the increase of terahertz frequency, the intraband polarization does oscillate downwards and its intensity decrease. Taking In0.52Al0.48As/InAs and Ga0.7Al0.3As/GaAsAs/GaAs superlattices for examples, because of the nonlinear effect of terahertz field and WSL excitons, their optical absorption spectra take on satellite peak structures. However, when these two superlattices in different states are compared, it’s concluded that the optical absorption spectrum anastomoses well for the strong coupling effect between the excitonic state of n<0 and the state of n=0, while a red shift emerges in the state of n=0 and the sideband effect in the optical absorption spectrum is not very obvious in the state of n>0.