This study aimed to evaluate changes in fusional vergence after strabismus surgery and to explore predictive parameters and the impact of fusional vergence on surgical outcomes. All patients diagnosed with intermittent exotropia (IXT) between March 2015 and October 2017 were included. Orthoptic assessments, including visual acuity, cover test, and mean fusional vergence (breakage/recovery, both negative and positive), were measured using a synoptophore. Subjects with symptomatic exotropia who underwent strabismus surgery were included. The primary outcome measure was the surgical success (SS) rate at a 6-month follow-up, with adverse effects such as over-correction and under-correction also evaluated. Data were analyzed using SPSS version 20.0. Surgical success was achieved in 62 patients (75.61%) at the 6-month follow-up. The postoperative fusional divergence breakpoints for the SS group and the surgical failure (SF) group were -7.52 +/- 4.14 degrees and -10.00 +/- 5.96 degrees (P = 0.040), respectively. The postoperative fusional convergence breakpoints for the SS group and the SF group were 10.03 +/- 4.36 degrees and 4.65 +/- 7.27 degrees (P < 0.001), respectively. The postoperative amplitude of fusional divergence was higher in the SS group compared to the SF group (P = 0.008). There was a significant difference in the duration of deviation (2.08 +/- 0.84 vs. 4.23 +/- 1.36, P < 0.001) between the groups, suggesting that the success rate of surgery is affected by the cumulative disease duration. Subjective deviation (-8.00 vs. -11.00, P = 0.049) and the amplitude of fusional divergence (6.52 +/- 4.10 vs. 4.80 +/- 2.59, P = 0.032) were also significantly different between the SS and SF groups. Postoperative breakpoints of fusional divergence and convergence, as well as the amplitude, were distinct between the SS and SF groups. Duration of deviation, angle of deviation, and subjective deviation were independent factors for (SS). Subjective deviation exhibited a predictive index for (SS) and may also reflect the severity of strabismus.