In this report, a CMOS-compatible colorimetric biosensor based on HRP/TMB/streptavidin system is proposed. HRP activity is used for labelled target quantification by photometric detector. The modulation of light intensity due to enzyme reaction can easily be detected in 96-well microarray plate by providing 650nm light source (LED). There is good correlation between absorbance in 650nm and the concentration of HRP-streptavidin with detection limit in 1.33 pM. This device is reusable and suits for various targets by microarray plate modification rather than biochip. With the advantage of portable, low cost, and reusable, this new designed immunosensor could be widely used for both research and diagnostic purposes.