Porcine deltacoronavirus (PDCoV) is a newly identified enteric coronavirus that causes serious diarrhea and vomiting in pigs, leading to substantial economic losses globally. Studying the molecular interactions between virus and host proteins is crucial for developing new anti-PDCoV strategies. Here, the role and mechanism of lactate dehydrogenase B (LDHB) in PDCoV replication were investigated. LDHB suppresses PDCoV replication in a dose-dependent manner, whereas the knockdown of LDHB via RNA interference enhances virus proliferation in LLC-PK1 cells. Mechanistically, LDHB directly interacts with PDCoV N protein in the cytoplasm. LDHB mediated the autophagic degradation of PDCoV N protein, thereby inhibiting viral replication. To our interests, PDCoV infection or PDCoV N protein expression significantly reduces LDHB expression in cells. Further studies showed that PDCoV N protein, dependent on its LIR motif, binds to the LC3. It facilitates LDHB degradation, possibly as a strategy for viral evasion from host cell cytosolic defense mechanisms. Overall, the present study provided a novel regulatory mechanism of LDHB in PDCoV infection and suggested new avenues for the antiviral strategy. IMPORTANCE: This study elucidates the intricate interaction between the PDCoV N protein and LDHB within the context of viral infection and immune evasion strategies. By demonstrating that LDHB can suppress PDCoV replication through a novel mechanism involving the autophagic degradation of the viral N protein, the research highlights the potential of targeting such interactions for antiviral strategies. The findings not only expand our understanding of how PDCoV manipulates host cell pathways to its advantage but also open up new avenues for therapeutic interventions that could mitigate the impact of this and similar viral pathogens.