To elucidate the mechanism by which pipeline shear increases the gel point of crude oil treated with a polymeric pour point depressant (PPD), pipeline⁃shear simulation experiments were conducted on T crude oil based on energy dissipation theory. Microscopic observations combined with ImageJ image analysis were used to characterize wax crystal morphology before and after shearing. The results showed that, after the addition of 25 mg/kg of PPD and heat treatment at 50 ℃, the gel point of T crude oil decreased from -8 ℃ to -14 ℃. Following simulated pipeline transportation, the gel point of the treated crude oil increased to -5 °C, representing greater deterioration than that observed for untreated crude oil. Each high⁃speed shearing event increased the gel point of the treated oil by 3-4 ℃. Microscopic analysis showed that the PPD promoted wax crystal aggregation and growth through co⁃crystallization and adsorption, reducing the crystal count from 605 to 272 and increasing the mean crystal area from 5.58 μm² to 7.33 μm². However, shear disrupted the aggregated wax crystal structures, causing the crystals to redisperse; wax crystal number increased to 771, while average wax crystal area decreased to 1.36 μm². This increased the dispersion and surface energy of the system, leading to a higher gel point. These findings clarify the microstructural mechanism by which shear weakens the effectiveness of polymeric PPD treatment and provide a theoretical basis for assessing shear⁃related safety during the pipeline transportation of waxy crude oil.