We will use the RBF network to predict the index in the following chapter. Output layer of the RBF network is a linear weighted sum of mesosphere. So it is much faster and easier than BP network, and it has better result on nonlinear mapping. For comparing the difference easily, it is the same data which was used by us. So it is exactly the same data from the S & P 500, the date from the 3rd January in 2007 to 30th October in 2009, 714 trading days.