  The Higgs boson $H$ has the largest coupling to the top quark $t$ among the
standard model (SM) fermions. This is one of the ideal places to investigate
new physics beyond SM. In this work, we study the potential of determining
Higgs boson $CP$ properties at the LHC and future 33 TeV and 100 TeV $pp$
colliders by analysing various operators formed from final states variables in
$t\bar{t}H$ production. The discrimination power from SM coupling is obtained
with Higgs boson reconstructed from $ H\to \gamma \gamma$ and $ H\to b
\bar{b}$. We find that $t\bar{t}b\bar{b}$ process can provide more than
3$\sigma$ discrimination power with 300 $fb^{-1}$ integrated luminosity in a
wide range of allowed Higgs to top couplings for the LHC, the 33 TeV and 100
TeV colliders. For $t\bar{t}\gamma\gamma$ the discrimination power will be
below 3$\sigma$ at the LHC, while for 33 TeV and 100 TeV colliders, more than
3$\sigma$ sensitivity can be reached.
