Abstract: Drosophila lini has been described as a new species from Taiwan,China by Bock and Wheeler in 1972.This paper deals with postmating reproductive isolation among 11 isofemale line strains of Drosophila lini collected from China,I.e.Taiwan (TAW 3146.1),Guangdong (Dinghu Shan DHS 315,DHS 401,DHS 410,DHS 501,and Nankun Shan NKS 9212,NKS 9231);Myanmar (Maymyo MMY 307,MMY 326,and Rangoon RGN 3,RGN 206).The results of the cross tests indicated that no postmating isolation was found between Chinese strains including Taiwan population and Guangdong two populations (Dinghu Shan and Nankun Shan).Drosophila lini from Guangdong Province is the same species as originally described from Taiwan.Cross experiments between strains from Myanmar,MMY 307 or MMY 326 females and RGN 3 males did not produce fertile F1 hybrids,but the reciprocal cross produced fertile F1 hybrid females and sterile F1 hybrid males.These results showed that between MMY and RGN strains postmating isolation is stronger than that between any other strains.Cross tests between Chinese and Myanmar strains,F1 hybrid females were fertile but F1 hybrid males were sterile,except for between DHS 410 and RGN 3 or RGN 206,in this cross test no fertile F1 hybrids were produced.Cross tests between NKS 9212 males and MMY 307 or MMY 326 females,no fertile F1 hybrids produced also,in reciprocal cross,F1 hybrid female were fertile but F1 hybrid males were sterile like that between RGN 3 and MMY 307 or MMY 326.We conclude that postmating isolation of Drosophila lini sbetween Chinese and Myanmar populations and within Myanmar populations (between MMY and RGN) have occurred,three units were clear,that are TAW,DHS,NKS populations;MMY population and RGN population.But we can not confirm they are sibling species,because postmating isolation machnism are not complete and genetic distances are smaller compared with that of other species of melanogaster group according to our unpublished data of mtDNA analysis.