Terahertz (THz) integrated circuits is a promising platform to create low cost and efficient components for high-speed sixth-generation (6G) communication networks. One of the key components for this application is detectors and  mixers integrated on THz silicon waveguide. Graphene, due to its unique and tunable properties such as zero band gap, high charge mobility and low electronic heat capacity, has already demonstrated promise in free space THz  detectors, mixers and modulators development. Moreover, graphene photodetectors integrated on the waveguide have already been demonstrated in visible and near infrared regions. In this work we present an electromagnetic  model of graphene terahertz detector integrated on silicon waveguide. Graphene THz detector was designed for operation at 150 GHz and can be used in the nextgeneration wireless communications for an ultrafast on-chip THz  signal processing.