A method comprises adding reagent I to a sample to be detected, incubating to obtain a first detection sample, and detecting to obtain a first absorbance value A1 of the sample to be detected; adding reagent II to the first detection sample, incubating to obtain a second detection sample, and detecting to obtain a second absorbance value A2 of the sample to be detected; adding reagent I to a standard sample, incubating to obtain a first detection standard, and detecting to obtain a first absorbance value B1 of the standard; adding reagent II to the first detection standard, incubating to obtain a second detection standard, and detecting to obtain a second absorbance value B2 of the standard; and using A1 and A2, and B1 and B2 to obtain a concentration level of complement factor H in the sample to be detected.