A pixel structure of a CMOS image sensor pixel structure and a manufacturing method thereof. The structure comprises a photosensitive element (37) and a multi-layer structure of a standard CMOS device arranged on the silicon substrate (31). A deep groove (38) having a light-transmitting space therein is formed above the photosensitive element, a side wall of the deep groove is surrounded by a light reflection shielding layer (39) continuously arranged in a longitudinal direction to reflect the light incident on the light reflection shielding layer. The side wall of the deep groove is surrounded by metal interconnects, vias, contact holes and polysilicon in annular configurations, thus the incident light on the deep grove is substantially completely reflected, which avoids the optical crosstalk and effectively improves the optical resolution and sensitivity of the pixel and the performance and reliability of the chip.