The research of plant genome has been transferred from the structural genomics focusing on determining the complete sequences of the genome to the functional genomics focusing on elucidating the biological function of genes. Now cloning differential expressed genes is of prime interest in molecular biology. In the past ten years, some methods used for studying changes of gene expression in plants have been developed. The authors review the developments of techniques and studies for the plants related gene cloning in RNA level and expound their principles, technical routes, improved methods, advantages and defects. Moreover, their applications and prospects in plants related studies are discussed.