Despite the considerable amount of recent studies about the systems of zhan-tian 占田, ke-tian 課田 and zu-diao 租調, under the Western Jin dynasty 西晉, most of the studies focus on deciphering the existing literature, but pay hardly any attention to the actual condition of agricultural production on which the formation of the above systems were based in that time. Hence this article attempts to re-assess the systems based on my recent research of the zu-diao system under the Wei dynasty from the viewpoints of labour cultivating capacity and productivity per mu 畝. It can be concluded as follows. Actually, zhan-tian means neither the limitation of private land holdings or the procedure of approving private land holdings as previous studies suggested nor the rule allowing every person to hold certain area of land, but the regulation over the cultivated land managed by the original agriculture officer 典農官 in that time. Also, ke-tian is not the official land distributed to the peasant and its cultivation is compulsory or semi-compulsory as recent studies asserted but a land tax upon the peasant according to the unit of mu. In other words, it is a kind of tax. Thus there was no cultivated land called zhan-tian nor ke-tian in the Western Jin dynasty. Despite the record that each man 丁男 is to be granted fifty mu of land as stated in the Chapter of Economy 食貨志 of the Jin History 『晉書』, and a fragment of Jin Gu-Shi 『晉故事』, it seems that a man was unable to cultivate such a large area of land in that time considering the labour cultivating capacity. Thus, it was probably a general principle laid by the government on the basis of farmer's cultivating capacity. Its ideal is consistent with the regulation over household tribute. On the other hand, the basic part of the zu-diao system was instituted early in the founding period of the Western Jin rather than the first year of Tai-kang 太康 when the Wu 吳 dynasty was recovered. Under the system, the household tribute 戸調 is levied according to the nine-rank principle 九品相通 (nine ranks are distinguished on the basis of household property), while the land tax 地租 is levied by referring to the actual size of cultivated land of each household. The tax rate is four dou 斗 per mu. Thus, the zu-diao system of the Western Jin dynasty is obviously inherited from the land and tribute system of the Wei dynasty 魏 (220-265), and is ideologically different from the zu-diao collection system after the implementation of the Jun-tian system 均田制 by the Northern Wei dynasty 北魏. It itself implies the consistency of the development of socio-economic system in the early medieval China.