Functional near-infrared spectroscopy （fNIRS） is noninvasive， portable， and suitable for measurements in natural environments. However， it still faces problems in practical measurements， including weak signals， difficulty in high-speed synchronous multi-channel acquisition， and inter-channel crosstalk. Therefore， this paper constructed a code-division photon-counting fNIRS system and designed a parallel measurement method based on code division multiple access. The system achieved high-sensitivity， low-crosstalk， high-speed synchronous multi-channel acquisition. Based on this system， this paper combined a steady-state visual evoked experimental paradigm to measure the hemodynamic responses of the visual cortex in myopic subjects under uncorrected and optically corrected conditions. It analyzed resting-state functional connectivity， task-related brain activation， and task-induced spatiotemporal dynamic features. The results show that the system can stably acquire multi-channel weak hemodynamic signals from the visual cortex and supports multidimensional characterization of brain functional response features under different visual conditions.