200 adults of Fraxinus mandshurica were selected from Qingshan seed orchard,Heilongjiang Province to screen primers which can result in different PCR products between male and female ash.PCR primers were designed based on the SSR sites of 5 423 ESTs of Fraxinus from NCBI and 179 502 sequences of F.mandshurica transcriptome from our lab.The results showed that:(1)9 488 and 3 557 SSR sites (174.96% and 1.98% in relative frequency,repectively) were found in ESTs from NCBI and transcriptome from our lab,respectively,with a dominancy of dinucleotide repeat in SSR type;(2)208 of 232 pairs of primer got PCR products,74 of which got different products between male and female and 27 of which got products with expected size;(3)After 3 rounds of PCRs,primer 19 and 56 got different products between two sexes in 64% and 89.5% trees,respectively.These results indicated that EST-SSR is a feasible method to identity the sex of F.mandshurica.