Abstract: Based on the definition simple beam, the finite element method is used to analyse some simple beams, with symmetric structure and loading, and symmetric beams, with different support. The calculation results show that there exists some horizontal displacements for simple beams in the symmetric plane but the symmetric beams have none and the stress states there are different too. This paper suggests that in order to simplify the calculation some finite element method books take one half of the simple beam for the calculating model, which is not sufficient.