A microcalorimetric technique based on bacterial heat-output was explored to evaluate the toxic effect of iron species on Escherichia coli. Power-time curves of the growth metabolism of Escherichia coli and the effect of different iron species on it were studied using the TAM III multi-channel microcalorimetric system, isothermal mode (stagnant), at 37±0.1°C. The differences in shape of the power-time curves and the thermodynamic and kinetic characteristics of E. coli growth have been compared. The dynamic parameters, that is, growth rate constant (k) and inhibitory ratio (I ) have been calculated. The experimental results reveal that the sequence of antibiotic activity of the different iron species (three forms) on Escherichia coli growth is Fe(III) (Ferric citrate) greater than Fe(II) (Ferrous chloride) greater than Fe(III) (Ferric chloride).These results are important to further studies of the physiology and pharmacology of iron species as antibacterial agents.