Alkaline phosphatase (ALP) of Helicoverpa armigera Hub. (Lepidoptera; Noctuidae) (GenBank accession No. EU729322) was cloned and expressed. The target gene H.a-ALP, having an open reading frame of 1608 bp, was reverse-transcribed from cDNA by the polymerase chain reaction. The open reading frame of the target gene was cloned into the pET-32a expression vector to obtain recombinant protein in Escherichia coli DE-3 cells for the subsequent production of polyclonal antibody. New Zealand white rabbits were used for production of anti-pET-32a-H.a-ALP. The production of antibody was also optimized by employing ELISA for titer determination. The produced antiserum was processed and used as an antibody. Western blot results showed that the polyclonal antibody produced was capable of effectively binding target protein not only from H. armigera but also from other lepidopterans such as Mythimna separata and Plutella xylostella.