Catechol is one of the most important intermediate products in the various pathways in degrading polycyclic aromatic hydrocarbons (PAHs). The ring cleavage can occur in two different orientations relative to the vicinal diols, and this difference in cleavage site is typically used to classify the catechol dioxygenases into two groups, the intradiol- and extradiol-cleaving enzymes. The essential process of intradiol pathway is the intradiol ring-cleavage catalyzed by catechol 1,2-dioxygenases. This paper summarized the research advances in these fields with the focus on the structure, enzymatic property and isoenzymes of the catechol 1,2-dioxygenases.