With the development of structural and functional genomics, nowadays specific plant genome and transcriptome sequences can be cloned much easier and faster. Next step is to identify the functions of different genes and regulating elements to unravel the genetic mechanisms behind plant growth and development. Expression and its regulation are the language and dynamic property of genetic material, so expression and regulation analysis of target genes and sequences in plant cell is the basis for function study. Besides stable genetic transformation, plant transient expression system gains broad application in recent years, and its combination with other new technologies as gene shuffling, VIGS and RNAi plays a more and more important role in plant functional genomics.