In order to investigate the effect of inhibitors on L-threonine biosynthesis in Escherichia coli, we have constructed a metabolic network model of amino acid biosynthesis from L-aspartate to L-threonine by using available informations from literatures and databases. In the model, the effects of inhibitors on the biosynthesis of L-threonine was included as an appropriate mathematical form. For simulation study, we used initial values as L-aspartate 5 mM, ATP 5 mM, NADPH 2 mM, and observed the concentration changes of intermediate metabolites over concentration changes of respective inhibitors. As a result, we found that concentrations of intermediate metabolites were not significantly changed over concentration changes of L-lysine, L-methionine, and L-glutamate. But, there were considerable changes of intermediates over concentration changes of L-serine, L-cysteine, and L-threonine, which can be considered as essential effectors on L-threonine synthesis. Contrary, the synthesis of L-threonine seems to be not related to the amounts of L-aspartate, and inversely proportional to the accumulated amount of D,L-aspartic β-semialdehyde.