  We report the results of a pilot study of CO$(4-3)$ emission line of three
{\it WISE}-selected hyper-luminous, dust-obscured quasars (QSOs) with sensitive
ALMA Band 3 observations. These obscured QSOs with $L_{\rm bol}>10^{14}L_\odot$
are among the most luminous objects in the universe. All three QSO hosts are
clearly detected both in continuum and in CO$(4-3)$ emission line. Based on
CO$(4-3)$ emission line detection, we derive the molecular gas masses ($\sim
10^{10-11}$ M$_\odot$), suggesting that these QSOs are gas-rich systems. We
find that three obscured QSOs in our sample follow the similar $L'_{\rm CO}-
L_{\rm FIR}$ relation as unobscured QSOs at high redshifts. We also find the
complex velocity structures of CO$(4-3)$ emission line, which provide the
possible evidence for gas-rich merger in W0149+2350 and possible molecular
outflow in W0220+0137 and W0410$-$0913. Massive molecular outflow can blow away
the obscured interstellar medium (ISM) and make obscured QSOs evolve towards
the UV/optical bright, unobscured phase. Our result is consistent with the
popular AGN feedback scenario involving the co-evolution between the SMBH and
host galaxy.
