Secondary Recrystallization Process in 3% Si-Steel was observed with EBSD technique in order to clarify the mechanism of unique growth of (110)[001] grain. The process is composed with three stages, I, II and III. The first stage is the slight development of texture and grain size, and the second is rapid growth of secondary grain. Both stages were found dominated by grain boundary mobility characterized by neighbor grain orientations. Compating two types of models, High Energy Boundary and Coincidence Site Lattice, the former could better explain the phenomena. At the second stage, grain growth was dominated not only by grain boundary characterization but also by the size difference of neighbor grains. Therefore, there were a lot of small grains having completely different orientations from those of secondary grains inside secondary grains after secondary recrystallization At the third stage, these small grains vanished during the higher temperature annealing. These results are well explained from the viewpoint of grain boundary mobility and size difference of neighboring grains.