西周时期的社会阶层可以分为天子、诸侯、卿、大夫、士等，其中士阶层中身份较低的成员和士以下的社会阶层构成了中低阶层。虽然西周时期实行世卿世禄制度，但是统治者的尚贤意识和任贤行为仍然为中低阶层里贤者的向上流动提供了空间。他们可以通过他人推荐、学校教育、在射礼中的突出表现、建立军功、自我推荐来实现向上流动。西周时期中低阶层中贤者之外也有一些相关人员能实现向上流动，他们的流动途径有忠实地执行王命、与贵族联姻等。

In the Western Zhou Dynasty, social classes consisted of the sovereign(tian-zi), dukes(zhu-hou), ministers(qing), bureaucrats(da-fu) and scholar-officials(shi), etc., among which scholar-officials in lower positions and those classes lower than scholar-officials belonged to the middle and lower classes. Although the Western Zhou Dynasty adopted the hereditary system that resisted social mobility, the practice that rulers promoted the capable and virtuous and put them in important positions had provided space for upward mobility in ways of being recommended, performing outstandingly in school or shooting ritual, gaining military merits and self recommendation. Some other people in the middle and lower classes could also have opportunities to move upward due to loyal execution of orders, marriage with aristocrats, and so on.