The invention provides a CMOS image sensor and a manufacturing method. The CMOS image sensor comprises a P-type substrate, a P-type epitaxial layer and a plurality of pixel units, wherein the P-type epitaxial layer is formed on the P-type substrate, an N-type buried layer, a P-type clamping layer, the P-type buried layer and the P-type epitaxial layer form a clamping photodiode, the N-type buried layer, the P-type clamping layer and the P-type buried layer are all formed in the P-type epitaxial layer, the P-type clamping layer is formed above the N-type buried layer, the P-type buried layer is embedded into the N-type buried layer, the P-type buried layer comprises at least two P-type sub-buried layers, and the at least two P-type sub-buried layers are distributed in the depth direction of the P-type epitaxial layer. By using the P-type buried layer formed in the N-type buried layer, the width of a depletion region of the clamping photodiode is expanded, the PN junction capacitance is increased, and the quantum efficiency and the full well capacity of the pixel unit are improved, so that the sensitivity and the imaging performance of a pixel unit are improved, the N-type buried layer is easier to deplete before exposure, and the reset noise is reduced.