Abstract: The Feulgen-DNA contents of amyloplasts in cotyledon cell of broad bean in sub-cellular level have been determined by microphometry and the result showed the dynamic change in different developmental periods.The amyloplasts DNA of copies increase with the developmental stage-The average of amyloplasts DNA content is 2.14(arbitrary unit) in the middle stage of growth.Amyloplasts DNA increase to 10.12 (arbitrary unit) in the mature period of cotyledon cell of broad bean.Amyloplasts DNA content in cotyledon cell of mature period is 9.6 times than that in the middle period of growth.The change of variability DNA contents among plastids showed normal distribution in natural logarithm by biological statistics.