To study the effect of dimethyl fumarate on early development of Zebrafish(Danio rerio), embryos at different developmental stages were treated with various concentrations of dimethyl fumarate. Morphological abnormalities were observed and Median lethal concentration at 24 h(24 h LC₅₀),48 h LC₅₀ and 72 h hatching rate were calculated. Effect on the blood vessel development was studied as well. The results indicated that dimethyl fumarate affected early embryo development in a dose-dependent manner and this adverse effect was related with the embryonic stage. The 24 h LC₅₀ of dimethyl fumarate for 2 hpf (hours post-fertilization), 10 hpf and 24 hpf embryos were 13.33 μmol/L, 17.98 μmol/L and 32.50 μmol/L, respectively, and 48 h LC₅₀ were 13.31 μmol/L, 16.35 μmol/L and 22.50 μmol/L, respectively. Embryo hatching rate at 72 h decreased after long term treatment with low concentrations of dimethyl fumarate. Dimethyl fumarate at concentration of 27.5 μmol/L significantly reduced the expression level of vascular endothelial growth factor 2.