  Most recently, both BaBar and Belle experiments found evidences of neutral
$D$ mixing. In this paper, we discuss the constraints on the strong phase
difference in $D^0 \to K\pi$ decay from the measurements of the mixing
parameters, $y^\prime$, $y_{CP}$ and $x$ at the $B$ factories. The sensitivity
of the measurement of the mixing parameter $y$ is estimated in BES-III
experiment at $\psi(3770)$ peak. We also make an estimate on the measurements
of the mixing rate $R_M$. Finally, the sensitivity of the strong phase
difference at BES-III are obtained by using data near the $D\bar{D}$ threshold
with CP tag technique at BES-III experiment.
