Cracks appeared in concrete structure is always concerned in construction engineering. As the cracks appear, the rigidity of structure will descend. So only the combination of slip theory and the non-slip theory could reflect the development of cracks in the course of analysis of cracks development. For axial tension and bending components, stiffness changes before and after cracking. The continuous beam with equal span is analyzed under the temperature load by the finite element method. As the cracks with different space appear, there is an abrupt bending moment with every crack. Different crack spacing, crack steep drop differently. So the wider the crack’s space is, the higher the abrupt bending moment is.