The perfect treasures of large seal Jian tcmmoku wares for tribute towards the end of Northern Song Dynasty have not been found to date. Several sherds have been unearthed successively in the Jian tcmmoku kiln site since the late eighties. Based on the nine samples, this paper studies their vessel shapes, engraving or stamping method of the characters of "Gong Yu" and " Jing Zhan". The chemical composition of bodies and glazes have been determined by XRF method and the comparison with those of common Jian tcmmoku wares has also been made. The microstructurc of bodies and glazes of the samples have been studied by means of POM and TEM. It has been pointed out that the following two formation mechanisms of Jian hare's fur glazes arc the same with that of common Jian tcmmoku wares, one is CAS2 →liquid phase separation→ crystallzation of iron oxide and the other is liquid phase separation in the glaze melt→crystallization of iron oxide . This paper especially illustrates that the reason why the black glaze and white hare's fur for tribute, which takes the greenish-black Jian tcmmoku with the sharp and stright white streaks as the best, is due to the surface reflection effect and inner scattering effect of incident rays caused by the crystallization of CAS2 on or near the glaze surface.