  The resonances ($\eta_c,\chi_{c0,c2}$) contribution to two-photon exchange
(TPE) effects in $e^+ e^- \leftrightarrow p \bar{p}$ is calculated in a simple
hadronic model. The calculation shows the TPE contributions by resonance
$\chi_{c2}$, which are dependent on the unknown phases $\phi_{E,M}$ of proton's
time-like form factors $G_{E,M}$, are much larger than the TPE contributions by
non-resonance and are comparable with measurement precision of coming PANDA
detector at $\sqrt{s} \sim M_{\chi_{c2}}$ for most $\phi_{E,M}$.
