The invention discloses a recombinant blue-green algae, which is prepared by a method comprising the step of introducing genes related to butanol synthesis shown in (1) and (2) into yhe chroococcaceae blue-green algae, wherein (1) the genes related to butanol synthesis comprise encoding genes of the following enzymes: electron transfer flavoprotein A subunit, enoyl hydrase, butyryl-COA dehydrogenase and alcohol dehydrogenase; and (2) the genes related to butanol synthesis comprise encoding genes of the following enzymes: electron transfer flavoprotein B subunit, the enoyl hydrase, the butyryl-COA dehydrogenase and the alcohol dehydrogenase. The invention realizes the blue-green algae to transform inexhaustible solar energy and greenhouse gas carbon dioxide on the earth into the energy product butanol, avoids wasting grains and other organic matters in the energy regeneration process, and at the same time is beneficial for environment protection. Therefore, one of ideal methods for realizing the sustained and healthy development of clean and renewable energy sources is to utilize the recombinant blue-green algae of the invention to produce the butanol.