  We consider a model in which dark matter is a composite baryon of a dark
sector governed by $SU(3)$ gauge theory, with vector-like quarks also charged
under $U(1)_Y$. The model provides simple answer to the dark matter stability
problem: it is a result of the accidental dark baryon number conservation. And
with an analogy to QCD, all physical quantities of the dark matter can be
calculated by rescaling the QCD experimental results. According to the thermal
freeze-out mechanism the mass of the dark matter is predicted to be
$\mathcal{O}(100)$~TeV in order to achieve a correct relic abundance. Such
heavy dark matter is in general hard for detection due to small dark matter
number density in the universe. However, dark baryon number in our model is not
necessarily strictly preserved thanks to operators suppressed by the Planck
scale, and such decay operator results in a decay lifetime marginal to the
current detection bound. We show our model with $\mathcal{O}(10^{27})~s$ dark
matter decay life time can explain the AMS-02 anti-proton data, if it is
experimentally interpreted as an access, although some theoretical uncertainty
may weaken its significance. We also investigate other phenomena of this model
such as the extragalactic gamma ray and neutrino signatures.
