Abstract: In this paper the effects of frozen pretreatment and water boiling pretreatment on the quality of black garlic were studied, and then the mature time, reducing sugar content, amino nitrogen content, total phenolic content and 5-HMF content of black garlic in different pretreatment processes were analyzed. The results showed that the black garlic mature time by frozen pretreatment was 4 days shorter than those by water boiling pretreatment and the control group ( the untreated galic) . In these two treatments, compared with those of the untreated black galic, the reducing sugar content increased by 43.3% and 23.3%, total phenolic content increased by 14.7% and 9.3%, amino nitrogen content of the processed garlic increased by about 5.8%respectively, and the content of 5-HMF was 45.6% and 18.4% lower than that of the control group. Therefore, the effect of frozen pretreatment was better than water boiling pretreatment and the control group.