Abstract: Thermal healing processing of Q235 steel with La addition was carried out in order to study the healing mechanism. An inner crack was made by compressing a drilled hole on the sample. The microstructures of samples were analyzed by means of optical microscope and SEM. The results showed that two types of dissipative structures obtained during heating healing for low carbon steel. One type was the dissolution of lamellar pearlite in host and the other was the formation of structure at crack healing zone. It was proposed that low carbon steel with inner cracks was an open system far from the balanced state. The dissipative structure was produced during thermal healing due to the nonlinear condition for reaction diffusion, energy fluctuation, structure fluctuation and composition fluctuation.