The invention provides a physical index analysis method for phenotypic diversity of cabbage mustard, and relates to the technical field of phenotypic diversity analysis. According to the method, physical information of phenotypic data is deeply mined; relatively complicated and independent botanical trait evaluation is converted into simple physical evaluation; plant phenotypic characteristic information is re-mined from the perspective of physics; that is, nine botanical traits such as plant height, development degree, leaf number, leaf weight, main bolting stem length, main bolting thickness, main bolting weight, single plant weight and branch number are converted into three physical attribute indexes such as main bolting volume ratio, bolting leaf weight ratio and density, and analyzing, comparing and evaluating of phenotypic diversity are carried out according to physical attributes. The method has the advantages of simplicity, batch, directness and intuition, is suitable for preliminary analysis, comparison and evaluation of a large number of cabbage mustard variety resources, and the purposes of saving a large amount of time, manpower, financial resources and material resources, deepening perceptual knowledge, reducing a phenotypic diversity research threshold and objectively evaluating phenotypic diversity are achieved.