Objective: To understand the dynamics and significance of perceptual eye position (PEP) in patients with intermittent exotropia by comparing it with subjective squint deviation (SSD). Methods: In this case series study, patients with intermittent exotropia treated at Beijing Tongren Hospital from February to August 2017 were tested for SSD using a synoptophore and, at the same time, were tested for PEP using a computer-based visual perceptual test. A total of 120 patients who were identified by the above two tests were accepted as research subjects. Linear correlation analysis was performed to assess the horizontal eye positions of SSD and PEP. The detection rate of SSD in vertical eye deviation was assessed, and the distribution of vertical PEP was analyzed in nonvertical SSD. Linear correlation and regression analysis were performed to assess horizontal and vertical PEP. results: In the horizontal direction, the mean SSD was -8.1±5.3°, and the mean PEP was 332±233 pixels. The more SSD migrated outward, the greater was the horizontal PEP, with a linear correlation between them (r=0.383, P<0.001). In the vertical direction,the detection rate of SSD was 2.5%. Among the remaining117 patients with nonvertical SSD, 113 patients were identified with PEP. The mean amount was 22±29 pixels, with 67.5%(81/120) of patients in the range of 1~26 pixels (≤0.5°) and 82.5%(99/120) in the range of 1~53 pixels (≤1°). The mean vertical PEP of the 120 patients was 24±32 pixels. There was a linear correlation between the vertical and horizontal PEP (r=0.373, P<0.001). The linear regression equation was vertical PEP=6.403+0.052×horizontal PEP (F=19.093, P<0.001). conclusions: In patients with intermittent exotropia, both SSD and PEP can reflect the deviations of the horizontal position of the eyes in the binocular deviated gaze state, but the detection rate of PEP in the vertical direction is much higher than that of SSD. The vertical PEP increases as the horizontal PEP becomes larger. PEP is a more sensitive and more comprehensive test of eye position deviation.