Amorphous polymers are viscoelastic materials. When they are subjected to dynamical loads, their behavior can be modeled by transform functions of stress and strain in the complex plane. In our work, a model based on the fractional calculus concept is proposed in order to predict the viscoelastic behavior of polymethylmethylacrylate (PMMA) over a wide temperature range between (Tg-190°C) and (Tg+15°C). The extended fractional solid model is shown to be capable of describing experimentally observed dynamic viscoelastic behavior over a wide temperature range, including multiple relaxations, using a limited number of free parameters. Structural recovery of PMMA was studied by dynamic mechanical spectrometry, and its effect on the different parameters is also discussed. Furthermore, from the fractional differential and fractional integral formulations. most of the relevant viscoelastic functions that quantify the degree of molecular mobility of amorphous polymers, likeE(t),E*(τ). andH(t), can be derived analytically.