The orthogonal function approach is developed in this paper to solve the Takagi-Sugeno (TS) fuzzy-model-based dynamic equations. The new method simplifies the procedure of solving the TS-fuzzy-model-based dynamic equations into the successive solution of a system of recursive formulae only involving matrix algebra. Based on the presented recursive formulae, an algorithm only involving straightforward algebraic computation is also proposed in this paper. The computational complexity can therefore be reduced remarkably. An illustrated example shows that the proposed method based on the orthogonal functions can obtain satisfactory results.