Objective：To investigate the alterations in surface electromyogram（sEMG）of the tibialis anterior and gastrocnemius muscles during straight-line walking in Parkinson’s disease（PD）patients with freezing of gait（FOG），and their correlations with clinical features. Methods：Twelve PD patients with FOG，thirteen PD patients without FOG，and eleven healthy controls（HC） underwent clinical assessments，gait kinematics acquisition，and sEMG evaluations during straight-line walking. The sEMG signal characteristics of the severely affected tibialis anterior and medial head of the gastrocnemius muscles during different phases of the gait cycle were analyzed using thenormalized root mean square（RMS）and co-activation ratio. Additionally，the correlations between sEMG alterations and clinical features were explored. Results：Compared to the HC and PD patients without FOG，PD patients with FOG exhibited slower gait speed，shorter stride length，reduced swing phase，and increased gait variability（P < 0.05）. During the single support phase of the gait cycle，the normalized RMS of the tibialis anterior in FOG patients was significantly lower than that of the HC （P < 0.05）. In the pre-swing phase，the normalized RMS of the tibialis anterior in the PD patients with FOG was significantly reduced compared to the PD patients without FOG（P < 0.01），while the PD patients without FOG showed elevated normalized RMS of the tibialis anterior compared to the HC（P < 0.01）. For the gastrocnemius，the normalized RMS during the pre-swing phase was significantly lower in the FOG patients compared to the patients without FOG and HC（P < 0.05）. Moreover，the co-activation ratio of the tibialis anterior and gastrocnemius during the swing phase was reduced in the FOG patients compared to the patients without FOG （P < 0.05）. In the FOG patients，the normalized RMS of the gastrocnemius during the pre-swing phase was significantly correlated with the severity of FOG（r=-0.758，P=0.007），as well as the co -activation ratio during the swing phase and stride length variability（r= 0.716，P=0.013）. Conclusion：The decreased sEMG activity of the tibialis anterior and gastrocnemius during the pre-swing phase， along with a reduced co-activation ratio during the swing phase，are key features of FOG in PD during straight-line walking.