The seedless red pulp pomelo of ‘Juxianghong’ was used as material and Anjiangxiangyou as control, to study the reason of seedlessness of ‘Juxianghong’ by observing the phenophase and floral characters, measuring the pollen activity and analyzing the variance of the growth of pollen tube of self–pollinationself and cross–pollination in the stigma with fruit seeds. The results showed that the phenophase of ‘Juxianghong’ was similar to the Anjiangxiangyou and was only two to three days difference; the developments of their floral organ were normal; the pollen germination rates of ‘Juxianghong’ and Anjiangxiangyou in stigma were 98.81% and 97.96% and their pollens had high activities (96.75% and 94.61%) and high fertility; the growth of pollen tube with cross–pollination was normal and reached the base of style after 120 h of pollination, while the growth of pollen tube with self–pollination began to decrease at 96 h and stopped at 120 h after pollination; there were no normal seeds in the fruits by self–pollination, while 103.8 normal seeds were found in the fruits by cross–pollination. Comprehensive analysis shows that self–incompatibility might be the main reason for the seedlessness of ‘Juxianghong’ pumelo.