The invention relates to a method for obtaining isoprene from a C5 fraction. The method is carried out in a division plate tower with two sections of division plates, wherein one division plate is arranged above the other division plate, and the two division plates are vertically arranged in the tower; the whole tower is divided into the following areas: an isoprene extracting and rectifying section, an alkyne extracting and rectifying section, a heavy component removing section, a commonly-used middle tower area, a solvent resolving section, an alkyne evaporating section, and a commonly-used lower tower area. The method completes two times of extraction and rectification operations and a part of heavy removing operations in a tower system, thus the energy consumption in the process of obtaining isoprene from a C5 fraction is reduced, the operation is simplified, the investment is reduced, and finally the product cost is reduced.