Objective To investigate the pelvic floor ultrasound parameters in relation to the severity of stress urinary incontinence (SUI) in the elderly women to provide reference for determining the degree of SUI in clinical practice. Methods Included in the study were 378 SUI patients treated in the Department of Ultrasound of the First Hospital of Xi′an Jiaotong University from January 2016 to January 2018, of whom 167 were mild (mild group), 114 moderate (moderate group), and 87 severe (severe group). Also, 100 elderly women without SUI who had physical check-ups in the same hospital were randomly selected as the control group. The pelvic floor ultrasound parameters were observed at rest and in Valsalva maneuver. Statistical analysis was performed using SPSS statistics 19.0. Depending on data type, comparison among groups was made by variance analysis, LSD-t test or Chi-square test. Results There were no significant differences among the four groups in baseline data. At rest, patients in all SUI group had thinker detrusor, wider posterior urethra-vesical angle, greater incidence of urethral funnel formation, but lower vertical distance between bladder neck and synchondroses pubis (BN-S) than those in the control group (P<0.05), the differences being statistically significant. There was no statistically significant differences among the SUI groups in the above parameters (P>0.05). In Valsalva maneuver, posterior urethra-vesical angle, urethral rotation angle, bladder neck mobility, incidence of urethral funnel formation increased significantly in the SUI groups as compared with the control group (P<0.05), and BN-S was significantly lower in the former than in the latter, the diffe-rences being of statistical significance (P<0.05). The bladder neck mobility increased with the severity of SUI, and the differences wereof statistical significance among the mild, moderate and severe groups[(25.18±3.82) vs (29.80±3.78) vs (33.13±3.60)mm, P＜0.05]. Conclusion Pelvic floor ultrasound can be used to observe the differences in the pelvic floor structures between the elderly women with SUI and those without, and bladder neck mobility differs in patients with SUI of different severity, providing a reference for determining SUI severity.