Abstract: In order to further know about the dynamic change and histological structure of splenic growth index of AA broiler, the weight and spleen index of AA broiler spleen were detected and the the size of spleen nodule, thickness of periarterial lymphatic sheath and size of central artery were observed by H· E staining and light microscopic by the writer. The results showed that during the whole experimental period, the spleen weight was always rising, and spleen index was crenellatedly increased and reached to the maximum when they were 49 days old, which indicated the immune function of spleen was best when they were 49 days old; the diameter of spleen nodule was largest when they were 14 days old, and the body fluid immune function of spleen was strongest at this time; the periarterial lymphatic sheath was thickest when they were 3 days old, and the cellular immunity of spleen was strongest at this time.