Recently studies indicate that the microcalorimetry is a suitable measurement for metabolic activities of organisms by recording the rate of heat outputs. In this work, we investigated the growth thermogenic curves of Escherichia coli (E. coli) affected by three kinds of Glycyrrhiza extracts by microcalorimetry. The powertime and exponential phase power-time curves of the E. coli growth at various concentrations of extracts were generated. The kinetic parameters such as the growth rate constants (C), maximum power outputs (Pm), peak times (Tm), and inhibition ratios were calculated and the relationships between Pm or Tm and C were established. Also, the clear correlations among the antimicrobial effects, Pm and C were obtained. The results revealed the Glycyrrhiza extracts had inhibitory activities towards E. coli while the Glycyrrhiza polysaccharides showed the most potent effects.