Abstract: In order to investigate the effect of low-dose α particle irradiation on primitive hematopoiesis in zebrafish embryos, the 5 h post fertilization (hpf) dechorionated zebrafish embryos were irradiated at doses of 0, 0.425, 0.85 and 1.7 mGy, respectively, by using ²⁴¹Am as the α particle irradiation source, the expressions of primitive hematopoietic markers gata1a and spi1b in the about 14 hpf zebrafish embryos were detected by the whole-in-situ hybridization (WISH), and that in the 22 hpf zebrafish embryos were analyzed by the real-time fluorescence quantitative PCR (qRT-PCR), and the variations of hemoglobin contents in the 48 hpf zebrafish embryos were measured by the O-dianisidine dyeing. It is found that for 0.425 mGy irradiation group, the expression of gata1a doesn’t significantly reduce （p>0.05）, the expression of spi1b slightly reduces（p<0.05）, and the hemoglobin content slightly decreases. For 0.85 mGy irradiation group, the expressions of gata1a and spi1b significantly reduce （p<0.01）, and the hemoglobin content also significantly reduces. For 1.7 mGy irradiation group, the expressions of gata1a andspi1b significantly increase （p<0.001）, and the hemoglobin content also significantly increases. The results show that α particle irradiation at dose of less than 0.85 mGy has an inhibitory effect on primary hematopoiesis in zebrafish embryos, while at dose of 1.7 mGy induces hormesis effect. Therefore, α particle irradiation at dose of 1.7 mGy can promote primitive hematopoiesis in zebrafish embryos.