The invention discloses a dual real-time fluorescent RT-PCR method for identifying and detecting a PRRSV classic strain and a highly pathogenic mutant strain, and an RT-PCR cation primer and a probe against the PRRSV classic strain and the highly pathogenic mutant strain for the method. Compared with the prior art, the method is characterized by rapidness, simplicity, strong specificity, high sensitivity and good reliability and can simultaneously carry out large batch sample analysis, and one-time reaction can identify and diagnose whether a sample is infected by the PRRSV classic strain or infected by the PRRSV highly pathogenic mutant strain or infected by the two strains, thereby providing a powerful technical support for monitoring and controlling a PRRS epidemic disease and having good application prospects.