Objective To study the pathomorphological changes and expression of hepatocyte growth factor （HGF） in the extraocular muscle in concomitant strabismus. Methods In a experimental study， 58 concomitant strabismus patients were recruited for the strabismus group and 10 normal subjects were recruited as the control group. Strabismus patients were divided into a concomitant exotropia group （32 cases） and a concomitant esotropia group （26 cases）. All the resected tissues of the rectus muscles were obtained from patients with concomitant strabismus during resection surgery and corneal implants. The mean average optical density of HGF was measured by the SABC method for immunohistochemistry using an image analyzer. The amounts of HGF in the resected muscles of patients were compared with normal subjects， and correlated with factors such as age and degree of deviation in the clinical data of the patients. Results ①The thickness of the cross-sectional area of muscle fiber in the resected rectus muscles of patients with constant exotropia was 308.9±68.4 µm2 and for patients with constant esotropia was 217.9±34.7 µm2， which were significantly lower than those of normal subjects （t=16.74， 28.34， P<0.05）. ②Masson staining showed that the weak side of the extraocular muscles of patients with concomitant strabismus had a decrease in the number of muscle fibers， an increase in collagen fiber content， and a disordered arrangement compared to the normal control group. ③The amount of HGF in the resected rectus muscles of patients with constant exotropia and constant esotropia were significantly lower than those of normal subjects （t=6.33， 4.75， P<0.05）. ④The amount of HGF was negatively correlated with age and the degree of deviation （r=-0.856， -0.525， P<0.05）. Conclusion A decreased level of HGF expression may contribute to the incidence of concomitant strabismus. The change in the expression of HGF in extraocular muscles may result in a deterioration of concomitant strabismus.