A self-regulated high-copy number plasmid containing chloramphenicol resistant gene, for the production of recombinant proteins under the regulation of bacteriophage ?pL promoter, was constructed. The designed 5024 base pair expression plasmid contained a heat sensitive repressor cI857 coding gene to regulate the function of ?pL promoter under heat shock induction. Using the constructed vector, for the first time, periplasmic production of human granulocyte macrophage colony stimulating factor (hGM-CSF) under heat induction was demonstrated. The developed hGM-CSF expressing system in this study has potential for the secretion of nearly 100% of expressed proteins into the Escherichia coli periplasmic space upon temperature up-shift.