In the paper we discuss the role of the axial U(1)A symmetry in the chiral phase transition using the U(Nf)R×U(Nf)L linear sigma model with two massless quark flavors.It is expected that above a certain temperature the axial U(1)A symmetry will be restored.A string-like static solution,the η string can be formed and detected in the ultrarelativistic heavy-ion collision process.
