The invention relates to a method for extracting and separating diolefins from C5 hydrocarbons by solvent circulation and azeotropic dehydration, pertaining to the preparation technology of extracting and separating isoprene from DMF. The invention is characterized in that: by employing a single tower, materials are sent into an extracting tower (1) from a feed port (6); at the temperature of 90-120 DEG C and tower top pressure of 0.02MPa, the azeotropic dehydration is carried out; and then the obtained material is taken out of a discharge port (7). In the process of employing the DMF method to separate diolefins from C5 components, the azeotropic dehydration method is adopted, which ensures that water containing in the extracting circulation solvent meet requirement; the water content is less than 500PPm, thus lowering the investment of equipment by reducing a tower system and an attachment heat exchanger, a machine pump and a liquid curing tank, and technology control difficulty is reduced; besides, the invention can guarantee that the water content in the circulation solvent meets requirements and the process of C5 separation can be carried out smoothly.