  The Planck Early Cold Cores Catalog (ECC) provides an unbiased list of
Galactic cold clumps, which form an ideal sample for studying the early phases
of star formation (\cite[Planck Collabrators et al. 2011]{Planck_etal11}). To
study their properties, we have carried out a molecular line
($^{12}$CO/$^{13}$CO/C$^{18}$O) survey towards 674 Planck cold clumps in the
ECC with the PMO 13.7 m telescope.
