Disclosed by the present invention is application of MARCO in screening PRRSV-resistant pigs. The study of the present invention shows that the expression quantity of MARCO in a pig body is closely related to the infection of PRRSV, the expression of MARCO is inhibited after PAMs are infected with PRRSV, the interference of MARCO promotes PRRSV replication, and the overexpression of MARCO inhibits virus replication; when the expression of MARCO is abnormally high in vivo, the pigs are resistant to PRRSV, otherwise the pigs are susceptible to PRRSV. Therefore, MARCO can be used as a new criterion to determine the susceptibility or resistance to PRRSV. The present invention lays a solid foundation for identifying susceptibility of pigs to PRRSV and screening and breeding of PRRSV-resistant pigs, has good clinical application value for screening and breeding of PRRSV-resistant pigs, has important significance for prevention and control of PRRSV, and is also conducive to breeding of superior strains of pigs.