We proposed a graphene based active plasmonic device by the introduction of graphene-MoS₂ heterostructures. The device was composed of a monolayer MoS₂ layer between the silicon substrate and periodically arranged graphene nanoribbon arrays. The finite-difference time domain (FDTD) method was used to analyze and compare the changes of the surface plasmon resonant wavelength and modulation depth (MD) in the two cases with and without MoS₂. It was found that all the parameters of the width, period and Fermi level of the graphene nanoribbons affect the surface plasmon resonant wavelength of the plasmonic device. The introduction of the monolayer MoS₂ can produce a redshift about 3 μm of the surface plasmon resonant wavelength, while the MD is basically unchanged. The redshift of the graphene surface plasmon resonant wavelength will provide application prospects for new active graphene plasmonic devices.