Under the background of the national “Double carbon” target, the heavy oil thermal recovery technology with the characteristics of” High energy consumption and high carbon emission” is facing the dual challenges of “Quality improvement, efficiency enhancement and energy saving and emission reduction”, developing high-efficiency cold recovery technology of heavy oil, such as polymer flooding and enhanced emulsion water flooding, has become the main replacement method at present. Water-soluble self-diffusion viscosity reducer can separate heavy oil molecules into small molecules, and make crude oil dispersed into small droplets free in water without changing the properties of crude oil. Water-soluble self-diffusion viscosity reducer can disperse crude oil into small droplets and free them in water, thus effectively reduce the viscosity of crude oil and improve the fluidity of crude oil. The viscosity reduction effect and self-diffusion experiment of self-diffusion viscosity reducer were evaluated by using super heavy oil and common heavy oil. The experimental results show that the viscosity of crude oil is greatly reduced by the viscosity reducer. For extra heavy oil, the viscosity reduction rate of 0.05% viscosity reducer solution can reach 98.65–99.73%. For common heavy oil, the viscosity reduction rate of 0.05% viscosity reducer solution can reach 72.2–83.2%. Through the evaluation of oil displacement performance, when the water cut is above 98%, the oil displacement efficiency can be increased by more than 10%. And The effect is better when water cut is lower after water flooding. The application of the water-soluble self-diffusion viscosity reducer provides technical support for further increasing heavy oil production after water flooding.