[Objective] To demonstrate the effects of water-soluble organic carbon in biochar for crop growth and quality and to open up new pathway for the application of biochar.[Methods] Three wheat straw biochar samples at 400℃, 450℃, 500℃ were prepared in laboratory, and corresponding water-soluble organic carbons were extracted with KOH solution to obtain biochar extracts of W₄₀₀, W₄₅₀, W₅₀₀. Furthermore, the extracts were applied in potted garlic test and the effects on garlic growth, quality and soil were measured.[Results] (1) W₄₀₀, W₄₅₀, W₅₀₀ had no significant effects on the growth of garlic. (2) W₄₀₀ treatment increased the content of garlic soluble sugar by 27.53%, increased soil organic matter and available phosphorus by 37%, 26%. (3) Garlic vitamin C, allicin content in the treatment of W₄₅₀ was significantly increased by 34.9% and 8.2%.[Conclusion] Biochar extract has no effect on the growth of garlic, but it can improve the quality of garlic.