The geometric properties of the Clifford Algebra including operations of the Clifford Product
the Projection and the Rejection are discussed in this paper.The Fourier Transform and its compute method in Clifford Algebra are introduced.Then the existence theorem of the Clifford Algebra is researches.Based on the existence theorem and the Clifford-Transform
the algorithm is proposed.The paper attempts to apply Clifford Algebra to handle the digital watermarking and the experimental results show that the algorithm has very good performance.