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Gravitational accretion accumulates the original mass, and this process iscrucial for us to understand the initial phases of star formation. Using thespecific infall profiles in optically thick and thin lines, we searched theclumps with infall motion from the Milky Way Imaging Scroll Painting (MWISP) COdata in previous work. In this study, we selected 133 sources of them as asub-sample for further research and identification. The excitation temperaturesof these sources are between 7.0 and 38.5 K, while the H_2 column densities arebetween 10^21 and 10^23 cm^-2. We have observed optically thick lines HCO+(1-0) and HCN (1-0) using the DLH 13.7-m telescope, and found 56 sources ofthem with blue profile and no red profile in these two lines, which are likelyto have infall motions, with the detection rate of 42\%. It suggests that usingCO data to restrict sample can effectively improve the infall detection rate.Among these confirmed infall sources, there are 43 associated with Class 0/Iyoung stellar objects (YSOs), and 13 are not. These 13 sources are probablyassociated with the sources in earlier evolutionary stage. By comparison, theconfirmed sources which are associated with Class 0/I YSOs have higherexcitation temperatures and column densities, while the other sources arecolder and have lower column densities. Most infall velocities of the sourceswe confirmed are between 10^-1 to 10^0 km s^-1, which is consistent withprevious studies.

In Search for Infall Motion in molecular clumps II: HCO+ (1-0) and HCN (1-0) Observations toward a Sub-sample of Infall Candidates