Objective: To analyse the impact of parity on pelvic floor morphology and function in postpartum period. Design: Retrospective study Setting: single-country . Population: This study included 1076 participants who visited Fujian Maternity and Child Health Hospital from December 2019 to August 2022. Methods: One-way ANOVA and covariance analysis were used between groups. Pearson correlation analysis and partial correlation analysis were used to assess the relationship between variables. Main outcome measures: Modified Oxford scale, surface electromyography, and pelvic floor three dimensions ultrasound. Results: Both one-way ANOVA analysis and covariance analysis indicated that the differences between primipara, deuteripara, and tertipara in bladder neck presentation, urethral rotation angle, bladder neck descent, and hiatal area were statistically significant. Pearson and partial correlation analysis all showed the positive correlations between rapid contraction, tonic contraction, endurance contraction and the grade of modified Oxford scale. Unlike pearson correlation analysis, most correlations subsided in the further partial correlation analysis except pretest resting baseline with urethral rotation angle. Conclusion: The grade of modified Oxford scale exhibited a positively correlation with the contractions of surface electromyography which reflected the reliability of pelvic floor surface electromyography. The impact of parity on not only the grade of modified Oxford scale but also surface electromyography was not statistically significant, but the descent of pelvic organ increased as parity increased. Except pretest resting baseline, any other factors of modified Oxford scale and surface electromyography had no correlation with pelvic organ displacement.