Quantum dots (QDs) have been widely used in biomedical and biotechnological applications.However, few studies focus on the assessing toxicity of QDs exposure in vivo.In this study, zebrafish embryos were treated with CdTe QDs (4 nm) during 4-96 hours post fertilization (hpf).Mortality, hatching rate, malformation, heart rate and QDs uptake were detected.We also measured the larval behavior to analyze whether QDs had persistent effects on larvae locomotor activity at 144 hpf.The results showed that as the exposure dosages increased, the hatching rate and heart rate of zebrafish embryos were decreased, while the mortality increased.Exposure to QDs caused embryonie malformations, including head malformation, pericardial edema, yolk sac edema,bern spine and yolk not depleted.QDs fluorescence was mainly localized in the intestines region.The larval behavior testing showed that the total swimming distance was decreased in a dose-dependent manner.The lowest dose (2.5 nM QDs) produced substantial hyperactivity while the higher doses (5, 10 and 20 nM QDs) elicited remarkably hypoactivity in dark periods.In summary,our data indicated that QDs caused embryonic developmental toxicity, resulted in persistent effects on larval behavior.