To improve the soluble expression of recombinant human interferon-$alpha$ that was directed by the araBAD promoter system of Escherichia coli, we attempted to control the overall protein expression rate via the addition of a repressor, methyl $alpha$-D-glucospyranoside($alpha$-MG). Recombinant interferon-$alpha$ was usually expressed as an inclusion body at the end of DO (dissolved oxygen)-stat fed-batch culture. However, the addition of 0.0025 to 0.01% $alpha$-MG after 0.5% L-arabinose induction effectively inhibited a tendency towards the formation of inclusion bodies, in which 67.6 to 73.1% of the expressed interferon-$alpha$ was found in the soluble fraction. It was likely that the addition of a repressor after L-arabinose induction partially modulated the transcription rate from the araBAD promoter system and changed the ratio of soluble and insoluble interferon-$alpha$ expression. This modulation might be considered as a method that can improve the soluble expression level of recombinant protein at the optimal temperature for cell growth.