Abstract: Corrosion-induced diameter reduction of reinforcing bars significantly diminishes the load-bearing capacity and reliability of reinforced concrete structures.This study employs synchrosqueezing wavelet transform (SWT) to extract the group velocity of guided wave for corroded rebar diameter evaluation.Initially,the L(0,1) mode is selected as the probing wave based on the propagation characteristics of guided wave.The optimal frequency is determined as 140kHz via the sensitivity analysis.The arrival time of the L(0,1) mode at the optimal frequency is precisely extracted by the SWT because of the high-resolution in time-frequency domain,enabling accurate calculation of the group velocity and assessment of the rebar diameter.To verify the feasibility and applicability of the proposed method,the accelerated corrosion tests of bare rebar and embedded rebar are conducted.The results of bare rebar tests demonstrate that the SWT could precisely determine the group velocity and effectively evaluate the rebar diameter.The results of embedded rebar tests show that the proposed method could evaluate the residual diameter of rebar after the debonding between the corroded rebar and concrete.