  The Cabibbo-Kobayashi-Maskawa (CKM) matrix elements $|V_{cd}|$ and $|V_{cs}|$
are essential to test the unitary of CKM matrix. Before 2014, many results of
$|V_{cd}|$ and $|V_{cs}|$ had been reported at BaBar, Belle, and CLEO
experiments. The precisions of the most accurate results of $|V_{cd}|$ and
$|V_{cs}|$ are 4.4\% and 3.3\%, respectively. After that, benefitting from
larger data samples collected at BESIII, the precisions of $|V_{cd}|$ and
$|V_{cs}|$ are improved to 1.8\% and 0.9\%, respectively.
