Abstract: Aluminum (Al)-induced release of organic acids from soybean roots has been regarded as one of important Al resistant mechanisms. The process is associated with energy consumption. However, the quantitative study of energy consumption remains to be elucidated in the process of Al-induced efflux of organic acids. In this study, two soybean (Glycine max) cultivars, Zhongdou 32(ZD 32) and Bendi 2(BD 2), were selected to study the mechanism of this process. The changes of secreted organic acids, cytoplasmic pH, adenylate, and inorganic phosphate concentration were examined in roots of soybean seedlings. The results indicate that Al of 25 mol/L could induce the secretion of malate and citrate from both cultivars roots significantly. Compared to the control, Al stress decreases the ATP contents by 40.1% and 13.2% in roots of ZD 32 and BD 2 respectively, and as well as increases the proton transmembrane electrochemical potential differences by 1711.8 and 570.6 J/mol. However, the inorganic phosphorus concentrations are not changed significantly in roots of both cultivars. Based on the above results, the Nernst-Gibbs equation is used to calculate energy consumption of organic acids secretion induced by Al. It is found that the gibbs free energy consumption amounts are 16.13 kJ/mol and 14.59 kJ/mol in ZD 32 and BD 2 roots, respectively. The energy consumption amounts for malate and citrate exudation are 0.96 kJ/mol and 3.15 kJ/mol in ZD 32, and 2.01 kJ/mol and 5.68 kJ/mol in BD 2 respectively. These finding suggests that different Al-tolerant soybean cultivars consume different energy in the process of Al-induced secretion of organic acids. This study provides a new way to screen Al-tolerant crop varieties.