  We have started a systematic survey of molecular clumps with infall motions
to study the very early phase of star formation. Our first step is to utilize
the data products by MWISP to make an unbiased survey for blue asymmetric line
profiles of CO isotopical molecules. Within a total area of $\sim$ 2400 square
degrees nearby the Galactic plane, we have found 3533 candidates showing
blue-profiles, in which 3329 are selected from the $^{12}$CO&$^{13}$CO pair and
204 are from the $^{13}$CO&C$^{18}$O pair. Exploration of the parametric spaces
suggests our samples are in the cold phase with relatively high column
densities ready for star formation. Analysis of the spatial distribution of our
samples suggests that they exist virtually in all major components of the
Galaxy. The vertical distribution suggest that the sources are located mainly
in the thick disk of $\sim$ 85 parsec, but still a small part are located far
beyond Galactic midplane. Our follow-up observation indicates that these
candidates are a good sample to start a search for infall motions, and to study
the condition of very early phase of star formation.
