The methylene blue(MB)solution was determined by mobile phone colorimetric method based on standard deviation transfer law.Through the relationship between the color primary color value RGB and the gray value Gr,calculated by the standard deviation transfer formula,the feasibility of the indirect measurement method was proved theoratically.The influences of three kinds of lighting environment on the quality of photos were analyzed,and three types of mobile phones were used as sampling tools.Results showed that the precision of indirect measurement method was significantly improved.The indirect measurement values XR,XG,XB of phone picture color showed a similar changing trend with methylene blue concentration.XB was proportional to the concentration C.A new method for the determination of methylene blue concentration was established.The recoveries for the method were between 91.3% and 101% with the relative standard deviations of 2.7%-4.8%.The stability,precision and accuracy meet the requirements for determination.