The effects of colchicine on in vitro microspore embryogenesis of Brassica napus were investigat- ed using 23 genotypes. 2.55 - 14.75 embryos/bud were regenerated from microspores of 3 genotypes by colchicine treatment at the concentrations of 10, 50 and 100 mg/L with 24 h or 48 h treatment but only 0.94 2.43 with 10 - 50mg/L for 72 h, indicating that the treatment of 72h has suppressive influence to microspore embryogenesis. The doses of 200 - 800mg/L colchicine with 16 -48h reduced 0.6 - 1.33 embryos/bud in 2 genotypes and 6.25 -9.36 in the untreated controls. Futhermore, the respone of microspore embryogenesis to colchicine is correlative with genotypes used. When appling 10, 20, 50 and 100mg/L colchicine and 48h treatment, lines 22B5-6 and 903-3 produced 37.09 - 69.47 embryos/bud, however 0.28 - 1.45 from genotypes F1- 29, W592 and SF10-12. The purpose of colchicine treatment microspore is dihaploid of microspore chromosome. Therefore, the colchicine dose and treatment duration used not only could produce a lot of embryos but also form higher rate of dihaploid plant. In present expriment using 10 - 50mg/L with 48h or 100mg/L with 24h obtained over 5 embryos/bud in about 80% of genotypes with more than 60% dihaploid plants. This suggested that our method can be used efficiently to the field of genetics and breeding in rapeseed etc.