Abstract: Synchronous Schistosoma japonicum egg granuloma in the lung of mouse model and PAP (peroxidas-anti-peroxidase) technique were employed to study the dynamics of antigen and antibody in the egg granuloma of S.japouicum and its relationship with the granuloma formation.The granulomatous response began on the 3.5 day after egg injection and increased to the maximal size at the 4th week.Lymphocyte populations and macrophage comprised an important part of lesions during the time of acute granulomatous response (7-28 day).Using PAP staining,the SEA within egg could be detected at high level on the first day after egg injection and then declined gradually.On the contrary,the SEA around egg was minimal at the first week and increased to the peak at the 4th week,then decreased gradually.No antibody could be detected throughout the experimental period (35 days).The results suggested that 1) the antigen of Schistosoma egg is the essential factor for the granuloma formation.2) S.japonicum egg granuloma could be formed in unsensitized mouse.3) The mechanism of egg granuloma formation of S.japonicum is similar to that of S.mansoni.