Abstract: Constructing full length cDNA library can obtain complete gene information to improve study of the functional genomics and overcome the shortage of the regular cDNA library. So, it has been regarded as an economical, rapid and effective way for functional genomic research, especially for organisms with huge genomes that are not amenable to whole genome sequencing. At present, the research of full length cDNA library has been developed, several methods of constructing the full length cDNA library have been built. In this paper, these methods were outlined and their advantages and disadvantages were compared, and their application was also mentioned.