Abstract: Marek’s Disease (MD) is one of the main infectious diseases that threaten the healthy development of the Chinese poultry industry. The evolution of epidemic strains of the MD Virus (MDV) in China is different from the evolution of strains overseas. The meq gene sequence of pathogenic strains is different from that of the attenuated vaccine strain (MDV-1). The meq and L-meq gene sequences of the MDV in the lymphoid tissue of chickens in latency period are homologous. The meq gene was only found in the lymphoid tissue of chickens during the onset period.