The microstructure evolution of the supercooling austenite for the eutectoid carbon steel during deformation was analyzed. The experiment results show that during deformation part of the supercooling austenite transformed to pearlite. The pearlite transformation began around the grain boundary. The interlamellar spacing of the pearlite was fine. In addition, the kinetics of the austenite to pearlite transformation during deformation was discussed in detail. The analysis indicates that the kinetics of the pearlite transformation under deformation can be described by the Avrami equation: . Particularly, in the Avrami equation the value b varied obviously with the change of the deformation conditions. However, the influence of the deformation conditions on the value n was little.