Objective: To investigate the differences of cardiovascular development in zebrafish after knockout of the hemoglobin gene on chromosome 3 and the underlying mechanism. Methods: We used CRISPR/Cas9 technology to knock out the fragment from hbba2 to hbae3 of the zebrafish hemoglobin gene on chromosome 3 to obtain heterozygous zebrafish (Hb+/-). The hemoglobin content and distribution of Hb+/- and wild-type zebrafish (WT) fertilized eggs were detected, the development of blood vessels was observed, and the number of 5-month-old erythrocytes of both were counted. The transcriptome of the heart of adult zebrafishes were analyzed by sequencing and validated by qRT-PCR. Results: Significantly reduced hemoglobin content in Hb+/-embryos and ectopic in 50 hpf embryos were detected. Compared to WT, Hb+/- has retarded development of abdominal major vessels and common cardinal veins in the abdomen, more rapid development of the subintestinal veins, and hyperplasia of the caudal intersegmental vessels. There was no significant difference in erythrocytes between Hb+/- and adult WT (P>0.05). Transcriptome analysis of the heart of adult zebrafish revealed that decreased hemoglobin levels led to up-regulation of NOX2 and NOS2, down-regulation of HIF3a, and activation of compensatory protective mechanisms in mitochondria. Conclusion: Hemoglobin gene knockout affects hemoglobin levels and vascular development in embryonic zebrafish, and the normal physiological activity of adult fish can be maintained by regulating gene expression and mitochondrial compensation mechanism. Understanding the regulation of hemoglobin production during embryogenesis and adulthood is important for the development of new therapies for anemia and cardiovascular disease.