The bacteriophage M13HEP was constructed by cloning the T7 RNA polymerase gene into phage M13mp18 RF DNA to express T7 RNA polymerase under the control of the lac promoter. Through M13HEP phage infection, T7 RNA polymerase could be introduced into an expression strain and heterologous genes under the control of the T7 promoter can be induced to express. Using this phage M13HEP induction system, many heterologous genes, especially some genes whose products are toxic to the host strain, were successfully expressed. By transferring F' pilli from E. coli XL1-blue to E. coli HMS174, a new E. coli strain HMS174F' was obtained to make the construction, expression, and single-stranded DNA rescue of the T7 expression plasmid be conveniently performed in the same strain.