The terahertz (THz) frequency region (0.1-10 THz) between microwaves and infrared, holds significant potential across various fields such as communication, sensing, and spectroscopy. Conventional THz systems for broadband emission and detection remain bulky and complex, making the development of a fully integrated, miniaturized THz system on a chip a significant challenge. Lithium niobate is an excellent material for THz emission and THz detection for its high second order nonlinearity and low optical losses in the near-infrared range [1]. Recently, thin-film lithium niobate (TFLN) platform has shown great potential for integrated THz systems [2-4]. Here, we develop a single device with dual functionalities based on the TFLN platform, capable of both THz emission and detection. Operating at the zero-dispersion wavelength (~1310 nm) for conventional single mode fiber, the system maintains short pulse duration without the requirement for complicated dispersion compensation methods, enabling broadband THz emission and detection from 0.1 to 2.5 THz.