Circular RNAs,which belong to non-coding RNAs,are so named for their circular shape. They stably exist in almost all kingdoms of life,accuring to be the most predominant transcripts instead of linear mRNAs. They act as regulators in transcription or posttranscription,playing important roles in tumors,cadiovascular diseases,neurodegenerative diseases and so on. In this paper,we collect information of the most authoritative articles,and elaborate the production,classification and molecular biologic characteri...