  We report measurements of the branching fractions for $\psi(3770)\to D^0 \bar
D^0, D^+D^-, D\bar D$ and resonance parameters of $\psi(3770)$ and $\psi(2S)$.
By analyzing the line-shapes of the cross sections for inclusive hadron, $D^0
\bar D^0$ and $D^+D^-$ event production in the range from 3.660 GeV to 3.872
GeV covering both $\psi(2S)$ and $\psi(3770)$ resonances, we extract the
branching fractions for $\psi(3770)$ decay into $D^0\bar D^0 {\rm and} D^+D^-$
respectively to be $B(\psi(3770)\to D^0 \bar D^0)=(46.7 \pm 4.7 \pm 2.3)%$ and
$B(\psi(3770)\to D^+ D^-)=(36.9 \pm 3.7 \pm 2.8)%$, which give $B(\psi(3770)\to
D \bar D)=(83.6 \pm 7.3 \pm 4.2)%$ and non-$D\bar D$ branching fraction of
$\psi(3770)$ to be $B(\psi(3770)\to non-D \bar D)=(16.4 \pm 7.3 \pm 4.2)%$. We
meanwhile obtain the resonance parameters of $\psi(3770)$ and $\psi(2S)$ to be
$M_{\psi(3770)}=3772.2 \pm 0.7 \pm 0.3$ MeV, $\Gamma^{\rm
tot}_{\psi(3770)}=26.9 \pm 2.4 \pm 0.3$ MeV and $\Gamma^{ee}_{\psi(3770)}=251
\pm 26 \pm 11$ eV; $M_{\psi(2S)}=3685.5 \pm 0.0 \pm 0.3$ MeV, $\Gamma^{\rm
tot}_{\psi(2S)}=331 \pm 58 \pm 2$ keV and $\Gamma^{ee}_{\psi(2S)}=2.330 \pm
0.036 \pm 0.110$ keV; as well as the $R$ value for the light hadron production
directly through one photon annihilation to be $R_{uds}=2.262\pm 0.054\pm
0.109$ in this energy region.
