Gene selection (feature selection) is generally pertormed in gene space(feature space), where a very serious curse of dimensionality problem always existsbecause the number of genes is much larger than the number of samples in gene space(G-space). This results in difficulty in modeling the data set in this space and the lowconfidence of the result of gene selection. How to find a gene subset in this case is achallenging subject. In this paper, the above G-space is transformed into its dual space,referred to as class space (C-space) such that the number of dimensions is the verynumber of classes of the samples in G-space and the number of samples in C-space isthe number of genes in G-space. it is obvious that the curse of dimensionality in C-spacedoes not exist. A new gene selection method which is based on the principle of separatingdifferent classes as far as possible is presented with the help of Principal ComponentAnalysis (PCA). The experimental results on gene selection for real data set areevaluat Gene selection (feature selection) is generally pertormed in gene space (feature space), where a very serious curse of dimensionality problem always existsbecause the number of genes is much larger than the number of samples in gene space (G-space). in difficulty in modeling the data set in this space and the lowconfidence of the result of gene selection. How to find a gene subset in this case is achallenging subject. In this paper, the above G-space is transformed into its dual space, referred to to as class space (C-space) such that the number of dimensions is the very number of classes of the samples in G-space and the number of samples in C-space is the number of genes in G-space. it is obvious that the curse of dimensionality in C-space does not exist. A new gene selection method which is based on the principle of separating different classes as far as possible is presented with the help of Principal Component Analysis (PCA). The experimental results on gene selection for real d ata set areevaluat