The invention discloses a multiplex-PCR (polymerase chain reaction) detection kit for bovine respiratory disease complex and a preparation method of the multiplex-PCR detection kit and relates to the field of detection of main viruses of bovine respiratory diseases. The problem that four pathogens of the bovine respiratory disease complex cannot be simultaneously and effectively detected in a multiplex-PCR method for detecting the bovine respiratory disease complex is solved. The kit comprises MightyAmp DNA polymerase, a 2xBuffe Mix buffer solution, sterile double distilled water, and four pairs of specific primers for identifying infectious bovine rhinotracheitis virus, bovine respiratory syncytial virus, bovine viral diarrhea virus and bovine parainfluenza 3 virus respectively, and also comprises positive control plasmids of the four viruses. The kit can simultaneously detect nucleic acids containing the four viruses in the same reaction system, is high in specificity and sensitivity and can accurately detect hosts and pathogenetic animals which suffer from invisible infection or continuously take viruses in the group of cattle, infectivity is avoided, the safety is high, the result can be detected in a short time, and time and labor are saved.