Abstract: In the coordinate Brassica napus L breeding work, the anthocyanidin relative content change was an important determination target. the author introduced a kind of improvement method of measuring anthocyanidin relative content in Brassica napus L seed coat .Compares with the commonly used HCl-methanol method, similarly did not need the standard sample, the cost is inexpensive, the determination simple quickly, simultaneously could in the effective elimination Brassica napus L seed coat the brown material to determine the result the disturbance, the obtained result could display the different luster accurately in the seed coat the anthocyanidin content change. pH differential method in simple, in quick foundation, determines the Brassica napus L seed coat anthocyanidin relative content to be more accurate, to be effective.