Graphene plasmons have attracted a lot of attention due to large confinement and small mode volume. However, the graphene-based plasmonic devices are still limited in the practical applications due to relatively small light absorption of graphene and limited light–matter coupling efficiency in general excitation strategy. Here, this work reported a strong plasmonic coupling effect observed in a novel graphene-Bi2Te3 heterostructure on the top of silicon gratings. It is interesting to find that the extinction spectra of the graphene-Bi2Te3 heterostructure has shown three times greater magnitude than that of graphene. This observation is mainly attributed to two factors: first, the coupling efficiency between the graphene and Bi2Te3 second, the higher light absorption in the graphene-Bi2Te3 heterostructure. Moreover, the plasmonic resonance peak of the graphene-Bi2Te3 heterostructure can be easily tuned by changing the grating period just like what happens in the graphene film. In all, this work utilizes the simple silicon grating to couple the light into the graphene-Bi2Te3 heterostructure, and further explores the hybridized Dirac plasmons in the graphene-Bi2Te3 heterostructure. We believe it will stimulate the interest to study the variant plasmonic heterostructure and trigger new terahertz device applications.