<p>The high water cut reservoirs in Daqing Oilfield are currently mostly developed using chemical flooding, and exploring the chemical flooding sensitivity of voids is of great significance. In this paper, firstly, four typical rock cores are selected to study the effect of water injection ratio on the pore throats of the rock cores. Secondly, the micro CT method was used to analyze the proportion of pore throat growth under different injection water ratios, thereby clarifying the characteristics of the influence of injection water on the micro pore throat structure. Thirdly, ternary composite chemical flooding is conducted and the microstructural characteristics of the pore throats affected by ternary composite chemical flooding is studied. Results show that: (a) For core samples with different initial permeabilities, the functional relationship between porosity and water flooding multiple shows a linear growth characteristic. (b) As the initial permeability of the core increases, under the condition of a certain water flooding multiple, the percentage of final pore throat increase shows an increasing trend. (c)With the increases of chemical flooding ratio, the percentage of pore throat increase at first and then turns to decrease, and becomes negative and continuously decreases with the increase of chemical flooding ratio.</p>