  Recently, the CMS and ATLAS collaborations have reported a diphoton peak at
750 GeV in the RunII of LHC at 13 TeV. We assume that the heavy fourth
generation quark doublet $z,~y$ with $380 $GeV mass, and the width of $z,t$ is
much less $b$ quark. Then we show that the contributions of the $(z \bar z+y
\bar y)/\sqrt{2}$ bound state $\eta_{zy}(1S)$ to the diphoton measurements
through $\sigma (pp\to \eta_{zy}(1s)\to \gamma \gamma) $ are $
5.6^{+5.6}_{-2.8} {\rm fb}$ at $\sqrt S=13$ TeV. They are constant with the 750
GeV diphoton excess measured by the CMS ant ATLAS collaborations.
