Studies of Charmonium at BESIII

In recent years, lots of studies of charmonium decays have been performed at BESIII based on large data samples of $J/\psi$, $\psi(3686)$ and $\psi(3770)$. Recent results in searches for radiative transitions of $\psi(3770)$ and rare phenomena in charmonium decays, and studies of light hadrons structures and properties will be presented.