In this study, based on the high-temperature characteristics of Western China tight oil reservoirs, a phenolic-larch tannin, temperature-resistant, plugging agent was synthesized by changing the mass fractions of larch tannin, double cross-linking agent, and accelerator. Young’s modulus of the dispersed gel was directly measured by an atomic force microscope, and the macroscopic plugging performance was evaluated by a physical simulation experiment of the artificially fractured natural core from Western China tight oil oilfield, thereby establishing a mapping relationship between the two. Research indicates that the formula of the high-temperature-resistant tannin system optimized by the experiment is 3.0 % sulfonated   tannin + 3.0 % formaldehyde   cross ‐ linking   agent + 1.0 % phenol   cross ‐ linking   agent + 0.05 % MnS O 4   accelerator ; the mechanical strength of the tannin gel and its plugging performance have a linear relationship. When Young’s modulus rises from 18.74 to 63.89 KPa, the plugging rate rises from 94.11% to 97.44%.