<p>To investigate the bonding performance between polymer waterproof coating (PWC) and expansive soil, 40 groups of expansive soil pull-out tests under different working conditions were carried out in this study. The variables considered included soil water content (12–27%), soil density (1.6–2.0&#xa0;g/cm³), and PWC coating thickness (0.8–1.5&#xa0;mm). The effects of these factors on bonding performance were systematically analyzed and discussed. The results show that soil density has the greatest effect on bond strength (relative importance = 0.7010), followed by water content (0.2778), while the contribution of coating thickness is minimal (0.0212). Bond strength increases approximately linearly with increasing soil density and reaches a maximum of 0.244&#xa0;MPa at a soil density of 2.0&#xa0;g/cm³. With increasing water content, bond strength first rises and then declines, following a quadratic relationship, with a peak value occurring near the optimum water content (15.1%). As the coating thickness increases, bond strength shows a decrease followed by an increase, and the highest value is obtained at a thickness of 1.5 mm. To enable a convenient and rapid evaluation of the bonding performance between PWC and expansive soil under engineering conditions similar to those considered in this study, predictive equations for bond strength were developed from the test results for different cases. The pulled out soil body (failure-body) exhibited a “soil–nail” effect. The longer the length of the failure-body, the stronger the “soil–nail” effect, and the more conducive to the bonding of PWC with expansive soil. Based on these analyses, recommended parameter ranges for practical application are proposed: a soil density not lower than 1.8&#xa0;g/cm³ (degree of compaction not lower than 90%), a water content close to the optimum water content, and a coating thickness of 1.5&#xa0;mm. The findings provide a scientific basis for the engineering application of PWC in expansive soil projects.</p>