Understanding the genetic basis of phenotypic diversity is fundamental to evolutionary biology and selective breeding. The White Cloud Mountain minnow (Tanichthys albonubes) is a renowned ornamental fish, yet the genomic basis of its prized ornamental traits (e.g., golden body color and long-fin) remains poorly understood. Here, we present a high-quality chromosome-level genome assembly for T. albonubes, which has a size of 1067.12 Mb with contig and scaffold N50 values of 5.65 Mb and 41.71 Mb, respectively. A total of 1036.50 Mb (97.13%) was anchored into 25 pseudo-chromosomes. The genome is highly repetitive (53.48% repetitive sequences) and encodes 24 121 protein-coding genes. Based on this reference genome and whole genome resequencing data of 126 individuals from four populations (one wild population, one native hatchery population, golden strain and long-fin strain), we revealed that the golden strain originated directly from the native hatchery stock, while the long-fin strain was derived from a distinct wild lineage. By integrating window-based pairwise F_ST scans with GWAS analysis, we demonstrated that the golden body color is a monogenic trait, with chrna2b on chromosome 15 as a prime candidate. In contrast, we found fin elongation is a polygenic trait and identified four candidate genes (mosmob, tbx18, vwa8, wnt6b) and the hedgehog signaling pathway underpinned this long-fin phenotype. Our study provides fundamental genomic resources and unveils the genetic architecture underlying two striking ornamental traits of T. albonubes, offering crucial insights for its further selective breeding and conservation.