Abstract: To find a rapid and economic method for the determination of total anthocyanins from purple and black crops in nature, the anthocyanins were extracted from three different crops of black wheat, eggplant and grape by using acidic ethanol. The total anthocyanin content from the three samples was determined by retentate analysis with pH differential method and subtraction method. The results showed that there was no significant difference in the accuracy of the results between the two methods using for black wheat and grapes. It was found that the absolute value of the difference between the results of the two methods was less than the uncertainty of quality determination when the two kinds of samples were re- tested, indicating that pH differential method and subtraction method were both applicable to laboratory quantitative detection of anthocyanin from black wheat and grapes. The relative standard deviation of eggplant measured by pH differential method was 2.20%, the precision was better than that of the subtractive method. There was a case of 4 consecutive points rise for the eggplant anthocyanins detected value from the quality control chart, showing that the accuracy of eggplant peel anthocyanin test results was poor by using subtraction method. The retesting showed that the absolute value of the difference between the two results obtained by the subtraction method was 0.023 mg/g, which was higher than the uncertainty of the measurement result 0.011 mg/g, indicating that the test results of anthocyanin from eggplant by pH differential method were reliable, but the test results by subtraction method had some problems.