A stimulated Raman scattering (SRS) CMOS imager for biomedical application is presented. To extract the small SRS response under a large offset of ratio approximately 10^-5, a high-speed lock-in pixel is designed. Two steps of noise reduction technique successfully reduce the offset and low-frequency noise. An SRS CMOS imager chip implemented using 0.11µm technology achieved a detectable AC signal level under large DC offset to be smaller than ratio of 10^-4. This finding suggests that the detection of very small SRS signal of lipid and triglyceride is feasible.