The invention provides a preventing and treating method for citrus tristeza virus. The method comprises the following steps: S4, carrying out spraying and root-irrigation of a diluted biological plantprotection agent every 48-96 hours to citrus and carrying out root-irrigation and tree washing of the diluted plant protection agent, applying an efficient organic fertilizer and a liquid fertilizerat the same time, and carrying out operations continuously for 2-4 hours； S5, carrying out spraying and root-irrigation of the diluted biological plant protection agent every 10-20 days, and carryingout root-irrigation and tree washing of the diluted plant protection agent at the same time； and S6, fully spraying the diluted biological plant protection agent every one month finally and carrying out root-irrigation of the diluted biological plant protection agent at the same time.
