The presence of minimal residual disease (MRD) is an important prognostic factor for multiple myeloma, while copy number variation (CNV) is a widely accepted biomarker used for multiple myeloma (MM). Detecting MRD and monitoring clonal evolution by monitoring CNV using low-pass whole genome sequencing is promising due to its high analytical sensitivity. To evaluate the correlation between MRD detected by flow cytometry and low-pass whole genome sequencing, nearly 200 samples were collected for this study. We applied ultrasensitive chromosomal aberrations detection to detect CNV for each patient. The follow-up samples were then collected and sequencing used the same method.