Abstract: The biological character of flowering were studied in 33 ancient male ginkgo trees which came from main distribution areas of Ginkgo Boliba L in China. The results showed that the anther length of 33 ancient male ginkgo trees ranged from 1.53mm to 3.17mm and the average number was 2.54mm; the width of anther ranged from 0.63mm to 1.55mm and the average number was 1.01mm; the length of pollen ranged from 29.52μm to 36.82μm and the average number was 33.49μm; the width of pollen ranged from 13.69μm to 15.99μm and the average number was 15.23μm; the ratio of pollen productivity ranged from 12.90% to 36.65% and the average number was 23.66%; the vitality of pollen ranged from 53.77% to 84.37% and the average number was 73.42%; variance analysis indicated that differences in all indexes of among 33 ancient male ginkgo trees were significant at 0.01 level except for the ratio of pollen productivity. The result of correlation analysis to 10 indexes showed that the number of flower spikes on short shoot, the anther number of flower spikes and the length of flower spikes could be used as indexes to evaluate the ratio of pollen productivity of male ginkgo trees.