OBJECTIVES: Freezing of Gait (FOG) is one of the disabling symptoms in patients with Parkinson's Disease (PD). While it is difficult to early detect because of the sporadic occurrence of initial freezing events. Whether the characteristic of gait impairments in PD patients with FOG during the 'interictal' period is different from that in non-FOG patients is still unclear. METHODS: The gait parameters were measured by wearable inertial sensors. Exploratory factor analysis was used to investigate the inherent structure of diverse univariate gait parameters, with the aim of identifying shared characteristics among the gait variables. RESULTS: This cross-sectional study involved 68 controls and 245 PD patients (167 without FOG and 78 with FOG). The analysis yielded six distinct gait domains which were utilized to describe the impaired gait observed during the "interictal" period of FOG. Both PD-nFOG and PD-FOG groups exhibited significant impairments in the pace domain, kinematic domain, gait phase domain, and turning process domain compared to the healthy control. The gait phase domain was different in the PD-FOG group compared to the PD-nFOG group (p corrected = 0.004, Cohen's d = -0.46). And it was identified as independent risk factor for FOG (OR = 1.64, 95% CI = 1.05-2.55, p = 0.030), as well as other risk factors: gender (OR = 2.67, 95% CI = 1.19-5.99, p = 0.017), MDS-UPDRS IV score (OR = 1.23, 95% CI = 1.10-1.37, p <
0.001), and PIGD subscore (OR = 1.50, 95% CI = 1.30-1.73, p <
0.001). The model demonstrated a correct discrimination rate of 0.78 between PD-FOG and PD-nFOG, with an area under the receiver operating characteristic curve (AUC) of 0.87. CONCLUSIONS: FOG was found to be associated with abnormal alterations in the gait phase domain during the interictal period. Models constructed using gait phase domain, PIGD subscore, gender, and severity of motor complications can better differentiate freezers from no-freezers during 'interictal' period.