Objective To investigate the effects of gefitinib on early embryonic development and expression of abcb4 tumor resistance genes in zebrafish.Methods Zebrafish were adopted as experimental animals and divided into gefitinib group,mixture of doxorubicin and gefitinib group and blank group.Zebrafish embryos of 0.5-1.5 hours after fertilization(0.5-1.5 hpf) were exposed to different concentrations of gefitinib,and then embryo development of zebrafish in 24-120 hpf was observed and the number of death,hatch and malformation was recorded.The embryo mortality was calculated under different concentrations of gefitinib at different time points,and the numerical value of IC50 was calculated;Hatching rates of zebrafish embryo in 48 hpf and 72 hpf and malformation rates of zebrafish embryo in 120 hpf were calculated.The zebrafish embryos exposed to different concentrations of gefitinib in different groups were collected,and the expressionof abcb4 gene in zebrafish embryos was detected by real-time quantitative PCR.Results Gefitinib IC50 in zebrafish embryos was 16.18 μmol/L.Compared with the control group,higher dosage (20 μmol/L) of gefitinib in other two groups significantly decreased hatching rates of embryos,and had obvious embryonic lethal effects and teratogenic effects.Moreover,the mRNA levels of the abcb4 gene in the zebrafish embryos of gefitinib group were not significantly changed,whereas the mRNA levels of the abcb4 gene in mixture of doxorubicin and gefitinib group were significantly different(P＜0.05).Conclusion Gefitinib has no significant effects on the expression of abcb4 tumor resistance gene in early development of zebrafish embryos(P＞0.05),but it can reverse the drug resistant effects of doxorubicin,suggesting that zebrafish can construct tumor resistance model.