Abstract: The somatic chromosomes in root tips, shoot tips, young leaves and anther wall of Seedless Wampee (Clausena lansium (Lour.) Skeels cv. ‘Yunan’) were observed and analyzed. The results showed that the chromosome numbers of somatic cells were varied. Among them were diploid (2n=2x=18), triploid (2n=3x=27) and aneuploid (2n=19~26). The aneuploid cell occupies the highest proporation of all the observation cells achieving 64.8%, next is the diploid cell 28.8%, and triploid cell accounts for 6.4%. The density and size of stomata and the shape of pollens of Seedless Wampee were compared with those of Chinese Wampee (Clausena lansium (Lour.) Skeels cv. ‘Jixin’), the results of which revealed that Seedless Wampee was the variation of diploid Chinese Wampee. Further more, the paper also discussed the relationship between the chromosome number variety and the seedless fruit.