To investigate the effects of chronic hypoxia on testicular development， this study employed histological observation and transcriptome sequencing to compare the microstructural and transcriptomic alterations in zebrafish testicular tissues under normoxic [（6.5±0.2） mg/L] and chronic hypoxic[（1.5±0.2）mg/L] conditions. Key findings revealed that chronic hypoxia induced disorganized arrangement of spermatogonia and significant reduction in sperm quantity under light microscopy. Transcriptome analysis identified 683 significantly downregulated（P<0.05） and 710 upregulated（P<0.05） genes in hypoxic testes. GO（Gene ontology） and KEGG（Kyoto encyclopedia of genes and genomes） enrichment analyses demonstrated predominant involvement of differentially expressed genes in pathways including muscle cell differentiation， response to oxygen-containing compounds， testis development， and amino acid biosynthesis. Notably， upregulated aco2 and downregulated idh3b expression patterns suggested their potential roles in hypoxia-impaired testicular development. The significant upregulation of energy metabolism-related genes （pgam2，aldoaa， aldoab） implied elevated energy demands for spermatogenesis under hypoxia. Furthermore， marked overexpression of muscle cell differentiation genes may represent an adaptive mechanism of male gonadal development to hypoxic stress. This study reveals testicular developmental regression in male zebrafish under chronic hypoxia and provides novel insights into the molecular adaptation of fish testes to prolonged hypoxic conditions through transcriptomic profiling.