Objectives The cause of abnormal morbidity and mortality in piglets in a pig farming enterprise in Guizhou Province was diagnosed to provide reference for preventing and controlling disease in pig farming enterprises. Methods The heart, liver, spleen, lungs, kidneys, lymph nodes and other tissues from 2 sick piglets aged 3-14 days were collected aseptically. Diagnosis was conducted with laboratory diagnostic methods including clinical observation, pathological dissection, isolation and culture of bacteria, and fluorescence quantitative PCR detection. Results There were symptoms including poor appetite, emaciation, and fever in affected pigs via clinical observation. There was peritonitis with gas accumulation in the intestines, congestion of mesenteric lymph nodes, gastric ulcer, and necrosis of the spleen edge via pathological dissection. No colonies were grown in the isolation and culture of bacteria. The results of fluorescent quantitative PCR detection showed that there was a significant exponential growth curve for porcine pseudorabies virus (PRV), porcine circovirus type 2 (PCV2), and porcine epidemic diarrhea virus (PEDV). No Ct value of foot-and-mouth disease virus, classical swine fever virus, porcine rotavirus, and porcine transmissible gastroenteritis virus was detected. Conclusions The dead piglets in the pig farm were infected with a mixture of PRV, PCV2, and PEDV. The main methods of prevention and control are vaccine immunization and improvement in biosafety protection.