Abstract: It's an important task to reduce the produce of the diacetyl during the beer's fermentation and prevent the reforming of diacetyl in ended beer.It is an effective method to the question of diacetyl to breed the diacetyl-less saccharomyces cereveseae by using the technology of laser induced mutation.In proper time and dosage,irradiating saccharomyces cereveseae with He-Ne laser as an induced mutation illuminant,can obtain a strain of diacetyl-less saccharomyces cereveseae.When the beer is made with this strain,the amount of diacetyl is 0.1253 mg/L,30% less than before.