The work aims to develop a new compound lactic acid fermented beverage of barley and guava through lactic acid bacteria fermentation combined with the functional and sensory advantages of barley and guava and analyze the flavor of the compound beverage in order to provide theoretical and practical basis for the utilization of barley and guava resources and the research and development of lactic acid beverage. In addition to taking the sensory score of lactic acid fermented beverage as the evaluation index, the mass ratio of guava-barley, fermentation time, fermentation temperature, addition amount of lactic acid bacteria and honey were also selected as the evaluation indexes. On the basis of single-factor experiment, the processing technology of lactic acid fermented beverage of barley and guava was optimized by orthogonal design. The order of the effects of various factors on the sensory score of lactic acid fermented beverage of barley and guava was as follows:fermentation temperature>addition amount of lactic acid bacteria> fermentation time>mass ratio of guava-barley. The optimum process conditions were as follows:the fermentation temperature was 38 ℃, the addition amount of lactic acid bacteria was 0.6%, the fermentation time was 28 h, and the mass ratio of guava-barley was 6∶4. Under these conditions, the active components of the fermented beverage were very well preserved, the taste was sour and sweet, the nutrition was rich, the state was uniform and stable, and there was no stratification. The sensory score was 96.6 points and the total acid content was 7.62 g/L. The optimum technological conditions of barley and guava lactic acid fermented beverage are determined by experimental analysis.