Abstract: The ninhydrin colorimetry was used to measure the absorbance of the bacterial cell lysis solution adsorbed on the surface of chalcopyrite during bacterial leaching. The influencing factors on the absorbance, such as measuring wavelength, lysing time, pH value of the solution, heating time and cooling time were investigated experimentally to get the optimal measuring conditions for the absorbance of the lysis solution, i.e., wavelength 560 nm, lysing time 25 min, pH value 7.0, heating time 15 min and cooling time 6 min. A standard curve showing the relationship between the absorbance and bacteria adsorption under optimal conditions was therefore given. It was found that the bacterial concentration is directly proportional to the absorbance of the lysis solution.