ObjectiveTo investigate the characteristics of electromyography (EMG) and postural stability of lower limb muscles during Y-balance test (YBT) and their relationship. MethodsFrom October to November, 2021, a total of 26 female students aged 18 to 22 years were recruited from Binzhou Medical University to complete YBT; while the EMG of rectus femoris, biceps femoris, tibialis anterior and gastrocnemius of supporting legs were collected synchronously to measure root mean square (RMS), integral electromyography (iEMG), and muscle contribution rate; and the postural stabilities were measured with three-dimensional force platform, to record total, antero-posterior (A/P) and medio-lateral (M/L) path length of center of pressure (COP). ResultsIn three directions of YBT, the RMS of rectus femoris was the most (χ² > 56.952, P < 0.001), and the iEMG and contribution rate of the tibialis anterior were the most (χ² > 38.507, P < 0.001). All the path length of COP was the shortest in the anterior (P < 0.05). In the anterior, the total path length of COP correlated with iEMG of biceps femoris (r = 0.452, P = 0.02) and gastrocnemius (r = 0.397, P = 0.045); in the postero-medial, the total path length of COP correlated with iEMG of gastrocnemius (r = 0.478, P = 0.014); and in the postero-lateral, the total path length of COP correlated with iEMG of tibialis anterior (r = 0.437, P = 0.026). ConclusionFor YBT, the activation of rectus femoris, tibialis anterior and gastrocnemius muscles of supporting legs are significant, and different with the indicators of EMG. Postural stability is the best in the posterolateral. The joint extensors or flexors play a different role for dynamic postural stability in the different directions.