In many new physics models, a color octet state could be coexist with the top partner and has stronger coupling with it. In the case of the top partner heavier than the color-octet, due to the interaction between top partner and top sector, after integrating out the top partner, it will induce the effective coupling between the color octet and top and then the color state could possibly mostly decaying into ttbar final states. Taking spin-0 color octet as an example, we find the effective coupling could induce large contribution from off shell top effects. It will affect a top tagging efficiency when the color octet is heavy (> 1 TeV). It also may provide some signature of the existence of the Top partner if we focus on the off shell region.