25ml lake water sample was mixed, centrifuged at 10,000rpm for 30 minutes. The supernatant was added NaCl to 0.5mol/L and mixed with 10% PEG6000 at 4 degrees C overnight; The solution was centrifuged at 8,000rpm for 30 minutes, and the precipitate obtained was enriched virus. Genomic DNA extraction kit was used to obtain environmental genomic DNA. The library was constructed directly by DNA-Seq library construction protocol.