The paper investigates the entanglement asymmetry in one-dimensional critical systems described by a Conformal Field Theory (CFT), focusing on its relation to non-topological defects. The entanglement asymmetry is a measure of symmetry breaking in a subsystem, quantified through the ratio of partition functions on Riemann surfaces with defect lines. For large subsystems, the partition functions are determined by the scaling dimensions of the defects. The main findings include: 1. **Subleading Contribution**: At criticality, the entanglement asymmetry acquires a subleading contribution scaling as \(\log \ell / \ell\) for large subsystem length \(\ell\). 2. **XY Spin Chain**: The XY spin chain, with a critical line described by the massless Majorana fermion theory, is used as an illustrative example. The corresponding defect is marginal, and the scaling dimension of these defects is related to the ground state energy of the massless Majorana fermion on a circle with equally-spaced point defects. 3. **Exact Expression**: An exact expression for the scaling dimension associated with \(n\) defects of arbitrary strengths is derived, generalizing a known formula for \(n = 1\). 4. **Prefactor of the Logarithmic Term**: The exact prefactor of the \(\log \ell / \ell\) term in the asymmetry of the critical XY chain is derived. The paper also discusses the asymptotic behavior of the entanglement asymmetry and provides numerical checks for the prefactor using exact lattice computations. The results highlight the importance of non-topological defects in quantifying symmetry breaking in critical systems.The paper investigates the entanglement asymmetry in one-dimensional critical systems described by a Conformal Field Theory (CFT), focusing on its relation to non-topological defects. The entanglement asymmetry is a measure of symmetry breaking in a subsystem, quantified through the ratio of partition functions on Riemann surfaces with defect lines. For large subsystems, the partition functions are determined by the scaling dimensions of the defects. The main findings include: 1. **Subleading Contribution**: At criticality, the entanglement asymmetry acquires a subleading contribution scaling as \(\log \ell / \ell\) for large subsystem length \(\ell\). 2. **XY Spin Chain**: The XY spin chain, with a critical line described by the massless Majorana fermion theory, is used as an illustrative example. The corresponding defect is marginal, and the scaling dimension of these defects is related to the ground state energy of the massless Majorana fermion on a circle with equally-spaced point defects. 3. **Exact Expression**: An exact expression for the scaling dimension associated with \(n\) defects of arbitrary strengths is derived, generalizing a known formula for \(n = 1\). 4. **Prefactor of the Logarithmic Term**: The exact prefactor of the \(\log \ell / \ell\) term in the asymmetry of the critical XY chain is derived. The paper also discusses the asymptotic behavior of the entanglement asymmetry and provides numerical checks for the prefactor using exact lattice computations. The results highlight the importance of non-topological defects in quantifying symmetry breaking in critical systems.