Graphene has the excellent characteristics of low defect density， easy large-area transfer and high carrier mobility. However， the zero-bandgap band structure of graphene leads to a short lifetime of photogenerated carriers， which restricts its application in highly sensitive photodetectors. In this work， ferroelectric material CuInP₂S₆（CIPS） was used as the top gate to control the photoelectric characteristics of graphene， and the possibility of improving the sensitivity of graphene terahertz detector was explored. The detection mechanism of graphene photothermoelectric effect and plasma wave effect under ferroelectric control was studied， and a high-performance graphene detector was obtained. At 0.12 THz， the responsivity of detector at room temperature reaches 0.5 A/W， with the response time of 1.67 μs and the noise equivalent power（NEP） of 0.81 nW/Hz^1/2 under a bias voltage of 40 mV and a gate voltage of 2.12 V. At 0.29 THz， the responsivity is determined to be 0.12 A/W， and a NEP is 1.78 nW/Hz^1/2. This work demonstrates the great potential of two-dimensional ferroelectric heterostucture at THz band.