The invention provides a method for producing lycopene through fermentation. According to the invention, blakeslea trispora (+) and blakeslea trispora (-) strains are adopted, and slant culture is carried out. Culturing is carried out for 6-7 days under a temperature of 26-28 EG C in an incubator; after 36-46h of seed culturing, fermentation culture is carried out; betaine is added for a first time, and fermentation culture is carried out for 100-120h under a temperature of 26-28 DEG C and under a rotation speed of 200-250r/min; a blocking agent is added when fermentation is carried out for 42h, and betaine is added for a second time; and fermentation is continued until finished. A fermentation broth is filtered, and wet thalli are collected. Through vacuum lyophilization, dried thalli comprising lycopene are obtained. According to the invention, with the added betaine, thalli respiratory chain system can be effectively promoted, and thalli oxygen consumption rate can be improved. Also, osmotic pressure respiratory depression upon the thalli during the fermentation process can be effectively relieved, oxygen delivery rate can be accelerated, and energy consumption can be reduced. thalli growth rate and lycopene content are improved, and production cost is reduced. According to the method, the operation is simple. Betaine has no toxic or side effect, and is convenient and safe to use. The method is suitable for industrialized productions, and has high application values.