In order to investigate the relation of muscle fiber MyHCs change and evoked potential of each subvolume of the lateral gastrocnemius muscle in rabbits at different postnatal ages，Each subvolume of lateral gastrocnemius muscle in rabbits at postnatal ages were examined by applying the clectronic stimulation instrument and sodium dodecyl sulphatepolyacrylamide gel eletrophoresis（SDSPAGE）.The results indicated that only the intermediate subvolume's peak voltage was basically uniform，but the lateral subvolume and the medial subvolume were separately some change. At the same time，it could be seen that grown rabbit's duration was longer than infancy in spite of which subvolume. This was greatly related with the component proportion of fiber types of each subvolume. And eletrophoresis bands of myosin heavy chain isoforms（MyHCs）of each subvolume of the lateral gastrocnemius muscle in rabbits showed respectively MyHCsⅡa，MyHCsⅡd（Ⅱx），MyHCsⅡb and MyHCs I. They corresponded to the muscle fiber phenotype typeⅡA（FOG），ⅡX（FO），ⅡB （FG）and I（SO）fiber.So

the relation between difference of function，the composition of muscle fiber MyHCs and phenotype were approached during postnatal development.