Abstract: The differences about the development of embryoids and calli arising from microspores were investigated in isolated microspore culture with eleven carrot accessions. After cultured about 92 days，five accessions began to form embryoids or calli. 70198 and 80Q54 produced both，the productions of embryoids were 10.56 and 7.00 per dish，and the productions of calli were 3.56 and 8.38 per dish，respectively. 90234 only produced embryoids，and the production was 6.75 per dish. 70Q78 and 80Q52 only formed calli，and the productions were 3.00 and 1.00 per dish，respectively. Microspores with thin wall，size elongating 1.5–4.0 folds，and large vacuole would develop into embryoids. Firstly they latitude split，arranged in series and connected tightly each other. While the microspores expanding like globe shape，splitting and connecting loosely would grow up to calli. The ploidy level of 137 regenerated plants from 70198，70Q78 and 80Q54 were detected using flow cytometry，and 68.6% were haploid，29.9% double haploid，and 1.5% triploid.

Key words: carrot, isolated microspore, embryoid, calli, ploidy