Porcine reproductive and respiratory syndrome (PRRS) is one of the most economically devastating viral diseases in the global pig industry. Recently, we isolated and plaque-purified porcine reproductive and respiratory syndrome virus (PRRSV) strain SC2020-1 from "aborted piglets" on a farm in Sichuan, China. To investigate the molecular biological characteristics of this strain, it was subjected to genome sequencing and analysis. The full-length genome sequence of strain SC2020-1 was 87.7% identical to that of the Lelystad strain (PRRSV type I protoype strain) and 82.2-84.8% identical to PRRSV type I isolates from China. NSP2, ORF3, and ORF4 were the most variable regions and contained discontinuous deletions or insertions when compared to other PRRSV type I strains. Phylogenetic analysis of the complete genome sequence showed that SC2020-1 clustered with PRRSV type I but outside of the three previously described branches (Lelystad virus-like, Amervac PRRS-like, and BJEU06-1-like). The Nsp2 gene was in the same branch with EUGDHD strains from China. This is the first report of PRRSV type I infection associated with abortion in sows in southwest China. Close attention should be paid to the prevention and control of this evolving virus.