  Deuterated molecules are valuable probes for investigating the evolution and
the kinematics in the earliest stages of star formation. In this study, we
conduct a comprehensive investigation by performing a single point survey of
101 starless clump candidates, and carrying out on-the-fly (OTF) observations
of 11 selected sources, focusing on deuterated molecular lines using the IRAM
30-m telescope. In the single-point observation, we make 46 detections for
DCO$^{+}$ J=1$-$0, 12 for DCN J=1$-$0, 51 for DNC J=1$-$0, 7 for N$_{2}$D$^{+}$
J=1$-$0, 20 for DCO$^{+}$ J=2$-$1, and 10 for DCN J=2$-$1. The starless clump
candidates (SCCs) with deuterated molecule detections exhibit lower median
kinetic temperatures and narrower H$_{2}$CO (1$_{(0,1)}$$-$0$_{(0,0)}$) median
full width at half maximum (FWHM) compared to those without such detections,
while simultaneously displaying similar median values of 1.1mm intensity, mass,
and distance. Furthermore, our OTF observations reveal that deuterated
molecules predominantly have peaks near the 1.1mm continuum peaks, with the
DCO$^{+}$ J=1$-$0 emission demonstrating higher intensity in the deuterated
peak region compared to the DCN and DNC J=1$-$0 emissions. Additionally, the
majority of emissions from deuterated molecules and $^{13}$C$-$isotopologues
exhibit peak positions close to those of the 1.1mm continuum peaks. By
analyzing the 20"$\times$20" regions with strongest deuterated emissions in the
OTF observations, we estimated deuterated abundances of 0.004$-$0.045,
0.011$-$0.040, and 0.004$-$0.038 for D$_{\rm frac}$(HCN), D$_{\rm
frac}$(HCO$^{+}$), and D$_{\rm frac}$(HNC), respectively. The differential
detection of deuterated molecular lines in our OTF observations could be
attributed to variations in critical densities and formation pathways.
