A method was developed for the detection of protein concentration with a smart phone confirming the parameter for image colorimetry,which was used to determine the concentration of reactants in different colors.The linear correlation coefficient of the proposed method was higher than 0.99,and the limit of detection(LOD) was 0.21 g/L.The detection performances of different brands of smart phones were investigated.Results demonstrated that the detection performances were basically independent from hardware configuration of smart phones.The repeatability of this method was also investigated.On detection of a single sample,the relative standard deviations (RSDs) for three concentrations of the sample were 2.0%,4.6% and 11.9%,respectively.Four samples were determined simultaneously,and the RSDs were 2.2%,3.8%,3.5% and 11.5%,respectively.The influences of brightness,color temperature and shooting distance were discussed.Results showed that brightness and color temperature were insignificant to detection,while the shooting distance could influence the detection results.The APP of smart phone was applied in the sample detection.The correlation coefficient(r2) between detection results of smart phones and spectrophotometer was 0.969.With the characteristics of high accuracy,high repeatability,portability and easy operation,the method could realize the fast detection on various products.