GeneHub software developed by us can be applied to evaluate the significance of expression similarity of genes in each functional unit of different gene function classification systems, and thus to select experiment condition related gene functional units. With different expression similarity measurement and different experiment data, we have applied GeneHub to analyze the expression correlation of functional related genes classified respectively with gene chromosome location, celluar location and interaction, metabolic pathway and signal transduction pathway relationship of protein products of genes. Genes classified according to these multiple ways all showed significant experimental condition related co-expression in our analysis. Our results provide further evidence for the assumption that functional related genes express similarly, which is widely adopted in gene expression profile analysis.