Circular RNAs (circRNAs) with a covalently closed loop structure which was different with linear RNAs, recently re-merged as novel regulator and exerted function in multiple biological processes. Through deep RNA sequencing (RNA-seq) technology coupled with bioinformatic analyses, a number of circRNAs has been identified. Moreover, circRNAs exhibit tissue- and development-specific expression indicating their potential biological significance. Actually, function of circRNAs as miRNA sponge has been well demonstrated in some diseases, besides, circRNAs also could function as RNA binding protein sponge and regulate alternative splicing and gene transcription. Notably, Emerging evidences showed that circRNAs played a pivotal role on the development of diseases including atherosclerotic vascular disease, neurological disorders and liver diseases, and served as diagnostic or predictive biomarkers of some diseases. This review mainly discusses the current advance of circRNAs as regulator involved in many diseases, and highlights circRNAs which have been well elucidated biological and pathogenic mechanism.