Objective To investigate the change in retinal protein kinase C (PKC) in form-deprivation myopia in the guinea pig. Methods Guinea pigs were randomly divided into three groups: 3-day deprivation, 7-day deprivation and 14-day deprivation. The right eye of 8 guinea pigs was deprived, and other eyes used as a control in each group. Form-deprivation myopia was induced with translucent eye shields on the right eye. Following a schedule, ocular biometric measurements (comeal curvature radius, refraction and axial length) were performed. The guinea pigs were sacrificed and retinal samples were obtained. Retinal PKC activity was detected by non-radioactive methods, and protein was evaluated by immunohistochemical staining. Results The deprived eyes in the guinea pigs became myopic with an elongation of the ocular axis dependent on eye occlusion. As deprivation time increased, there was an increase in the severity of myopia. Compared to the control eyes, retinal PKC activity was significantly up-regulated in the deprived eyes of each group (P<0.05). Retinal PKC activity was elevated after 3 days of occlusion [(0.28 ±0.08)units/ml, P<0.05], and reached a maximum after 7 days of occlusion [(0.43±0.10)units/ml, P<0.05]. Subsequently, a decline in retinal PKC activity was observed after 28 days of occlusion [(0.32±0.07)units/ml, P<0.05]. PKC protein was expressed in the retinal ganglion cells and inner nuclear layer. PKC protein was up-regulated in the inner nuclear layer of the retina in the deprived eyes (P<0.05), but there was no change in ganglion cells (P>0.05). The tendency for a change in retinal PKC activity coincided with the protein in the inner nuclear layer of the retina in the deprived eyes. There was a significant correlation between the intensity of PKC immunoreactivity in the inner nuclear layer and retinal PKC activity in the deprived eyes (r=0.994, P=0.000). Conclusion The increase in retinal PKC activity played an important role in the development of form-deprivation myopia in guinea pigs.