Abstract: 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6FAPB) and 3,3',4,4'-oxydiphthalic dianhydride (ODPA) were used as the monomers of polyimide (PI). Using the in-situ amination method, the graphene oxide (GO) was firstly reacted with 6FAPB to obtain the in-situ aminated GO. Then, the in-situ aminated GO was polymerized with ODPA and 6FAPB to obtain the in-situ aminated GO/poly(amic acid) (PAA) solution. After coating of the GO/PAA solution on a clean glass substrate, the in-situ aminated GO/PI composites containing 0.05wt%, 0.1wt%, 0.3wt%, 0.5wt% and 1.0wt% GO (mass fraction) were successfully prepared by thermal imidization. By means of FTIR, XPS, XRD, UV-vis, TGA, TMA, SEM, tension tester and contact angle measurement, the structure and properties of the in-situ aminated GO/PI composites were characterized. These experimental results show that the in-situ aminated GO connects with PI macromolecular chains with chemical bonds, which is helpful for improving the dispersion uniformity of GO in PI matrix and the interaction between GO and PI molecular. The XRD results show that the in-situ aminated GO/PI composites are amorphous. The optical properties of the in-situ aminated GO/PI composite films show a sharp downward trend, while the mechanical and thermal properties increase with the increase of GO loading. When the mass fraction of GO is 1.0wt%, the tensile strength of the in-situ aminated GO/PI composites increases from 64 MPa to 83 MPa, the Young's modulus improves from 1.67 GPa to 2.10 GPa, furthermore, the 10% thermal decomposition temperature also increases from 593℃ to 597℃. However, the glass transition temperature (T_g) of the in-situ aminated GO/PI composites changes slightly. As a result of thermal imidization, most of the oxygen functional groups on the surface of GO disappear, the water uptake of the in-situ aminated GO/PI composites decreases from 0.86% to 0.58%, and the water contact angle enhances from 72.5°of pure PI film to 77.8° of 1.0%GO/PI film.