  One of the most energetic gamma-ray bursts GRB 110731A, was observed from
optical to GeV energy range by Fermi and Swift Observatories, and by the MOA
and GROND optical telescopes. The multiwavelength observations over different
epochs (from trigger time to more than 800 s) showed that the spectral energy
distribution was better fitted by a wind afterglow model. We present a leptonic
model based on an early afterglow that evolves in a stellar wind to describe
the multiwavelength light curves observations. In particular, the origin of the
LAT emission is explained through the superposition of synchrotron radiation
from the forward shock and synchrotron self-Compton emission from the reverse
shock. The bulk Lorentz factor required in this model is $\Gamma\simeq520$ and
the result suggests that the ejecta must be magnetized.
