Tetracyclines are a class of antibiotics that exhibited potent activity against a wide range of Gram-positive and Gram-negative bacteria, yet only five members were isolated from actinobacteria, with two of them approved as clinical drugs. In this work, we developed a genome mining strategy using a TetR/MarR-transporter, a pair of common resistance enzymes in tetracycline biosynthesis, as probes to find the potential tetracycline gene clusters in the actinobacteria genome database. Further refinement using the phylogenetic analysis of chain length factors resulted in the discovery of 25 distinct tetracycline gene clusters, which finally resulted in the isolation and characterization of a novel tetracycline, hainancycline (1). Through genetic and biochemical studies, we elucidated the biosynthetic pathway of 1, which involves a complex glycosylation process. Our work discloses nature's huge capacity to generate diverse tetracyclines and expands the chemical diversity of tetracyclines.