  The theoretical debris supply rate from a tidal disruption of stars can
exceed about one hundred times of the Eddington accretion rate for a
$10^{6-7}M_{\odot}$ supermassive black hole (SMBH). It is believed that a
strong wind will be launched from the disk surface due to the radiation
pressure in the case of super-Eddington accretion, which may be one of the
mechanisms for formation of the envelope as observed in tidal disruption events
(TDEs). In this work, we explore the evolution of the envelope that formed from
the optical thick winds by solving the global solution of the slim-disk model.
Our model can roughly reproduce the typical temperature, luminosity and size of
the photosphere for TDEs. Based on \texttt{CLOUDY} modeling, we find that, if
only considering the radiation-driven disk wind, the emission line luminosities
are normally much lower than the typical observational results due to the
limited atmosphere mass outside the envelope. We propose that the ejection of
the outflow from the self-collision of the stellar debris during the
circularization may provide enough matter outside the disk-wind photosphere.
Our calculated spectra can roughly reproduce the main properties of several
typical emission lines (e.g., $\rm H\alpha$, $\rm H\beta$ and \ion{He}{2}),
which was applied well to a TDE candidate AT2018dyb.
