We use the Bethe's ansatz method to study the entanglement of spinons in the quantum phase transition of half integer spin one-dimensional magnetic chains known as quantum wires. We calculate the entanglement in the limit of the number of particles N → ∞. We obtain an abrupt change in the entanglement next the quantum phase transition point of the anisotropy parameter 1 ∆ = from the gapped phase 1 ∆ > to gapless phase 1 ∆ < .