The invention discloses ribonucleic acid interference (RNAi) for inhibiting porcine reproductiion and respiratory syndrome virus (PRRSV) replication and a preparation method of RNAi, The RNAi comprises a small interfering RNA (siRNA) sequence. The preparation method comprises the steps of constructing a short hairpin RNA (shRNA) slow virus expression vector, preparing replication-defective slow virus, infecting slow virus Marc-145 cells (green monkey kidney cells) and the like. The invention also discloses a method for verifying the effect of inhibiting PRRSV from replication. The RNAi sequence has the obvious effect of inhibiting the PRRSV replication on sensitive cells. According to the invention, the exploration of RNA interference on in vitro and vivo replication of hog cholera virus is carried out, a slow-virtue-mediated stably-integrated RNA interfering technology for special conserved gene segments of a targeted hog cholera virus genome is constructed, and transgenic animals with the siRNA of targeted hog PRRSV are hopeful to construct. The necessary experimental data is accumulated for gene function research of RNAi applied to PRRSV and prevention and treatment of hog cholera, and early-stage preparation is provided for disease resistance breeding of animals.