OBJECTIVE:To seek a handy method to quantitatively evaluate the missing of spiral ganglion neurons in delayed neuron death model in chinchillas. METHODS:15 adult chinchillas were divided averagely into three groups. Animals in group 1 were used as normal control. Animals in group 2 were sacrificed two months after coadministration of gentamicin (125 mg/kg) and ethacrynic acid (40 mg/kg). Animals in group 3 were terminated four months after gentamicin and ethacrynic acid injection. The cochleae were routinely embedded in Epon812 for cochlear sections. The number of spiral ganglion neurons in sections of Rosenthal’s canal at various locations was counted and statistically analyzed. RESULTS:The size of Rosenthal’s canal in cochlear hook region in chinchilla was bigger than that of the upper turns of the cochlea that containing more spiral ganglion neurons in the base. Two months after the cochlear hair cell removal, more spiral ganglion neurons missing was found in the hook. This suggested that the delayed spiral ganglion neuron missing might develops from the base of the cochlea with gradient towards apex. Four months after coadministration of gentamicin and ethacrynic acid, most spiral ganglions disappeared due to lacking neuronotrophins. CONCLUSION：Evaluation of cochlear spiral ganglion neurons in sections at Rosenthal’s canal at different locations is a reliable approach to quantitative observations.