Objective:To evaluate the therapeutic effect in guinea pigs with immune-mediated sensorineural hearing loss (IMSNHL) after the local implanting with bone-marrow mesenchymal stem cells (BMSCs) into inner ear, which was decorated with recombinant lentivirus vocters carrying interleukin-4 (IL-4) gene. Methods: Guinea pigs were immunized with keyhole limpet hemocyanin (KLH) and caused 33 animal models ,which were divided into three groups on refering to matched-pairs design. Recombinant lentiviral vector integrated IL-4 gene to infect the BMSCs in vitro,the green fluorescence report and the result of RT-PCR to confirm the successful infection of BMSCs. BMSCs decorated with interleukin-4 (IL-4) gene (group A )and without gene (group B) were implanted separately into scala tymani. Group C as control group were injected phosphate buffer (PBS). Auditory functions and the KLH level of Guinea pigs blood were monitored respectively by brain stem responses (ABRs) and ELISA test; Fluorography immunohistochemistry test was performed for tracing BMSCs and enzyme immunohistochemistry test for the situation of IL-4 gene express and productive protein distribution in inner ear. Hematoxylin-eosin (HE) stain and light microscopy were carried out. Results: There were no significant differences in level of KLH in blood serum 2 weeks after immunization (pretransplantation) and 1 week after the transplantation of the BMSCs in the same guinea pigs from each group. The threshold of ABR Ⅲ wave decreased in group A and group B,the result is more significant in group A and group B than that in group C (P<0.05).The results of immunohistochemistry test showed that Fluorescence positive BMSCs mainly scattered in scala tymani and scala vestibule. Enzyme immune-reaction positive product (i.e. IL-4 gene product) mainly located at spiral ganglion, Corti organ, stria vascularis ,around areas of BMSCs in cochlear duct and etc. After the transplantation of cells, the degree of immunity inflammatory rea