  Time-series photometric observations were made for the High Amplitude
$\delta$ Scuti star CW Ser between 2011 and 2012 at the Xinglong Station of
National Astronomical Observatories of China. After the frequency analysis of
the light curves, we confirmed the fundamental frequency of $f = 5.28677\
cd^{-1}$, together with 8 harmonics of the fundamental frequency, 7 of which
are newly detected. No additional frequencies were detected. The O-C diagram,
produced with the 21 newly determined times of maximum light combined with
those provided in the literature, helps to obtain a new ephemeris formula of
the times of maximum light with the pulsation period of $0.189150355 \pm
0.000000003\ days$.
