  We revise the Non-Gaussianity of canonical curvaton scenario with a
generalized $\delta N$ formalism, in which it could handle the generic
potentials. In various curvaton models, the energy density is dominant in
different period including the secondary inflation of curvaton, matter
domination and radiation domination. Our method could unify to deal with these
periods since the non-linearity parameter $f_{\rm NL}$ associated with
Non-Gaussianity is a function of equation of state $w$. We firstly investigate
the most simple curvaton scenario, namely the chaotic curvaton with quadratic
potential. Our study shows that most parameter space satisfies with
observational constraints. And our formula will nicely recover the well-known
value of $f_{\rm NL}$ in the absence of non-linear evolution. From the micro
origin of curvaton, we also investigate the Pseudo-Nambu-Goldstone curvaton.
Our result clearly indicates that the second short inflationary process for
Pseudo-Nambu-Goldstone curvaton is ruled out in light of observations. Finally,
our method sheds a new way for investigating the Non-Gaussianity of curvaton
mechanism, espeically for exploring the Non-Gaussianity in MSSM curvaton model.
