The ultra-low permeability reservoirs have poor physical properties，which leads to difficult fluid flow，often showing the characteristics of non-linear flow. In the past，the study on non-linear flow laws focused more on water flooding but less on CO₂ flooding. Considering the insufficient understanding of the non-linear flow laws of CO₂ flooding in ultra-low permeability reservoirs in Gao89 area of Shengli Oilfield，an experimental study in this regard was carried out to reveal the influence of the interaction between CO₂ and crude oil on the flow characteristics of crude oil. The calculation formula of the minimum threshold pressure gradient and the non-linear flow characteristic representation model of CO₂ flooding under different permeability were constructed. The results show that there is threshold pressure in CO₂ flooding in the ultra-low permeability reservoirs，and the minimum threshold pressure gradient of crude oil has a good power function relationship with fluidity. With the increase in fluidity，the threshold pressure gradient decreases significantly.In addition，the flow curve of CO₂ flooding shows the characteristics of two stages，i.e.，non-linear stage+linear stage. The flow velocity at the linear stage has a good linear relationship with the pressure gradient，and that at the non-linear stage has a good quadratic function relationship with the pressure gradient. CO₂ dissolved in crude oil has a significant swelling and viscosity reduction effect，which drastically lowers the minimum threshold pressure gradient of crude oil and enhances the flow capability of crude oil，and the non-linear stage in the flow curve is shortened.