  We review status of $R$ measurement and QCD studies at low energy range,
discuss prospects for a super $\tau-$charm factory in $2-7$ GeV. With a
high-luminosity $e^+e^-$ collider, statistics are no longer problem for $R$
measurement and a precision of $2\%$ or even better is foreseen, that will lead
to bring down the uncertainty of hadronic contribution to the QED running
coupling constant $\Delta\alpha_{had}$ and the anomalous magnetic moment of the
muon ($a_{\mu}$); measure the strong coupling constant $\alpha_s$ and the charm
quark mass; improve the measurement of the resonance parameters of heavy
charmonia. Huge data samples in $2-3$ GeV will make it possible to study
excited states of $\rho$, $\omega$ and $\phi$, or exotic $Y(2175)$; measure
electromagnetic form factor of mesons and baryons; and measure fragmentation
functions of hadrons.
