Objective:To clarify whether the signal peptide of human nerve growth factor can mediate secretory expression of beta-endorphin and whether there is difference between the efficiency of signal peptides from human and mouse nerve growth factor. Methods: Two kinds of eukaryotic vectors containing human or mouse signal sequence-mediated secretory expression of beta-endorphin were constructed.The culture supernatant and cells were collected 48 h after NIH3T3 cells were transfected by the two kinds of vectors, and the cover slips with single-layer cells was prepared. The concentration of beta-endorphin in the culture was determined by radio-immunoassay. The total RNA was extracted from cells and mRNA from fusion genes was assayed by RT-PCR. Cells on cover slips were subjected to immunofluorescence staining. Results: RT-PCR showed that the fusion genes were expressed in NIH3T3 cells; the expression of beta-endorphin was mainly in the cytoplasm of NIH3T3 cells. The concentrations of beta-endorphin in the supernatants 48 h after transfection with pcDNA3.1-hEP and pcDNA3.1-mEP were (280.33±24.16) pg/ml and (191.04±7.96) pg/ml (P<0.05), respectively, and they were significantly different from that of the blank control group (P<0.01). Conclusion: The signal sequence of human nerve growth factor can mediate the secretory expression of protein and the efficacy of human signal peptide is higher than that of mouse signal peptide.