The Kurdjumow -Sachs mechanism of martensite transformation is investigated in detail in this paper. The distortion matrixes of the first shear, the second shear and lineal adjustment according to the K-S mechanism are calculated. From the lattice distortion matrix, we can obtain invariant normal planes. According to the assumption that the habit plane is constructed with some of the invariant normal planes, the macroscopic habit plane (225)A is also discussed. The results show that the K-S mechanism can account for the relief effects, habit plane, orientation relationship and the change of structure.