OBJECTIVE Based on Logistics regression analysis to establish a four-dimensional ultrasound diagnosis model of postpartum stress urinary incontinence (PSUI). METHODS A total of 236 parturients who gave birth in our hospital from July 2017 to August 2020 were selected, and all were examined by four-dimensional pelvic floor ultrasound. According to whether there was PSUI within 3 months after delivery, women were divided into PSUI group and non-PSUI group. The age, pre-pregnancy body mass index, gestation times, parity, gestational age, mode of delivery, vaginal delivery, perineal lateral incision or laceration, newborn weight, and four-dimensional ultrasound parameters of the pelvic floor (BND, URA, PUVA, LHA) were compared between the two groups. Multivariate Logistic regression analysis was used to determine the influencing factors of PSUI. According to the regression coefficients of risk factors, a four-dimensional ultrasound diagnosis model of the pelvic floor was constructed, and ROC curves were drawn to analyze the diagnostic value of the four-dimensional ultrasound diagnosis model of the pelvic floor for PSUI. RESULTS PSUI occurred in 38 of 236 parturients, the incidence was 16.10%. There was no significant difference between PSUI group and non-PSUI group in age, pregnancy times, parity, gestational age, and perineal lateral resection (P>0.05). The pre-pregnancy BMI, percentage of vaginal delivery, newborn weight, BUD, URA, LHA, and Valsalva PUVA in the PSUI group were significantly higher than those in the non-PSUI group (P<0.05). Multivariate logistic regression analysis showed that pre-pregnancy BMI (OR=3.112, 95%CI: 1.478～6.552), delivery method (OR=2.776, 95%CI: 1.252～6.155), newborn weight (OR=3.721, 95%CI: 1.259～10.997), BUD (OR=4.412, 95%CI: 1.794～10.850), URA (OR=4.176, 95%CI: 1.809～9.640), Valsalva state LHA (OR=2.379, 95%CI: 1.217～4.650) , Valsalva state PUVA (OR=2.841, 95%CI: 1.117～7.226) is the influencing factor of PSUI (P<0.05). The variable corresponding to the smallest standardized β value (ie, the β value of the variable boundary of 0.867) among the influencing factors screened out by the multivariate logistic regression analysis is assigned to 1, and the other variables are divided by the β value by 0.867 and rounded to the nearest integer. The diagnosis model is constructed after the corresponding integer scores, with a total score of 0-6. The area under the ROC curve of model score diagnosis of PSUI was 0.903 (95% CI: 0.780~0.953), and the sensitivity and specificity of the cut-off value of 4.89 were 87.7% and 78.8%, respectively. The area under the ROC curve of BND in the diagnosis of PSUI was 0.843 (95% CI: 0.725 to 0.903), and the sensitivity and specificity with a cut-off value of 12.2 mm were 85.6% and 79.3%. CONCLUSION LHA and PUVA in BND, URA, Valsalva state are the influencing factors of PSUI, and the four-dimensional ultrasound diagnosis model of pelvic floor based on the above factors is better than BND alone in the diagnosis of PSUI.