The invention discloses a homologous recombination defective gene analysis method, which comprises the following steps of: 1, performing quality control and filtering on low-depth whole genome (sWGS) sequencing data by adopting fastp software, comparing the data to a human reference genome by adopting bwa software, sequencing the data according to a chromosome sequence by adopting gatk software, simultaneously marking and removing a repetitive sequence, and comparing the repetitive sequence with the human reference genome; qdnaseq software is adopted to analyze the copy number change in the genome, and shallowHRD software is adopted to evaluate HRD based on the copy number change of the genome and give a score. By accurately evaluating the instability of the genome, the positive detection rate of the homologous recombination defect can be effectively increased, and the detection cost is reduced; meanwhile, the method has the advantages of low time consumption, capability of being used for single sample analysis and the like, and is combined with BRCA1 / 2 gene variation; meanwhile, the depth requirements of gene variation and instability evaluation are met, so that the homologous recombination defect state of a patient is accurately judged, the detection cost is reduced, and the detection economic benefit is improved.