Abstract:By using Brassica campestris ‘Longyou 7’,‘Longyou 9’,‘winter juncea’ and Brassica napus ‘vision’ as materials,statistical analysis on stoma guard cell perimeter and chloroplast number were performed,SSR marker was used to test accuracy of counting chloroplast number and measure perimeter in stomatal guard cells further.(1)The variation of stoma guard cell perimeter between parents and interspecific hybrid was very similar among the different leaf positions on the same plant.However,the variation was relatively similar at the down location in the same leaf.(2)Parents and interspecific hybrid had a clear dividing line for perimeter of stomatal guard cell at 58.90 μm,75.83 μm.The chloroplast number of ‘Longyou 7’ and ‘Longyou 9’ should be at the range of 10 to 12;the chloroplast number of ‘Longyou 9’בvision’,‘Longyou 7’בwinter juncea’ should be at the range of 14 to 16;the chloroplast number of ‘vision’ and ‘winter juncea’ should be at the range of 18 to 19.(3)The accuracy of this method for identification interspecific hybrid was 97.5% after SSR marker test.Obviously,there is a specific boundry between stomatal guard cells perimeter and chloroplast number of B.campestris,Brassica napus,‘winter juncea’ and their interspecific hybrid which can be used to identify interspecific hybrid.If guard cell perimeter is at the range of 58.90 to 75.83 μm,and at the same time chloroplast number is at the range of 14 to 16,the plant will be true hybrid.