Focusing on morphological differences in the waist, abdomen, and hip regions of Chinese women, this study investigates the etiology of common crotch-structure defects in women’s trousers and proposes a systematic pattern-revision strategy. Through 3-D body scanning, manual anthropometry, and questionnaire surveys conducted on adult women from multiple regions, five typical somatotypes were identified. Using virtual try-on and parametric modeling, the study analyzed how key structural parameters—crotch depth, crotch width, and front-to-back rise differential—affect comfort and aesthetics. On this basis, a “morphology–structure–comfort–aesthetics” mapping model was constructed and employed for iterative pattern revision. Results indicate that targeted adjustments significantly alleviate issues such as crotch binding, fabric pooling, and tensile tightness, thereby improving wearability and offering a feasible pathway for personalized customization of women’s trousers.