In this paper, a fast classification algorithm which uses a table-look-up method is proposed. Both theoretical and experimental results are shown: (1) in two dimensional case the computation time can be reduced to the same order of time needed for the data I/O; (2) in the case of more than two dimensions more than half a computation time can be saved. The classification accuracy is not affected by the use of the table-look-up method. The algorithm is most suitable for computers without a floating-point processor.