Colourless polyimide (CPI) is widely used as covers, substrates and touch panels for flexible displays, which require high glass transition temperatures (Tg), low coefficients of thermal expansion, excellent optical transparency and good mechanical properties. CPI is mainly obtained by introducing fluorine-containing groups to change the chemical structure of the molecular chain. This method of preparation allows for the production of CPI with high light transmittance, although it concomitantly results in a reduction in thermal and mechanical properties. By modifying two-dimensional inorganic materials, the thermal and mechanical properties of CPI can be effectively improved. However, technical difficulties such as poor compatibility with CPI and the complicated modification process also limit the application of two-dimensional inorganic materials in CPI modification. Therefore, a new method for modifying of CPI by a two-dimensional organic polymer, a two-dimensional polyaramid (2DPA) was proposed in this study, 2DPA/CPI composite films were prepared by the solution phase mixing method and the two-step thermoimide method. The structure and properties of 2DPA were analyzed, and the effects of 2DPA additives on the properties of 2DPA/CPI composite films, such as light transmittance, water absorption, Tg, and tensile strength were investigated. The results showed that without compromising the light transmission, the best effect was achieved when the addition of 2DPA in 2DPA/CPI composite films was 1wt%, and the Tg was increased from 338℃ to 358℃ compared to that of CPI films. The tensile strength reached 71.44 MPa, and elongation at break reached 4.34%, which were increased by 21.37% and 24.36%, respectively; and the water absorption rate was reduced by 39%, from 3.33% to 2.03%. The successful preparation of this CPI composite modified with two-dimensional organic material offers new ideas for the research and application of high-performance CPI-based composite materials, holding significant research value.