Abstract：The affix ‘er' had various usages and underwent many broadening process in its usage during Jin and Yuan period. Based on six typical documents in this period, this paper makes a comprehensive study on its distribution, meaning and function. ‘er' in Jin and Yuan period was mainly used as suffix to noun, but other various usages also emerged, such as, used as suffix to verb, adjective, adverb, etc.‘er's meaning and function in rhythm is very remarkable. The interaction between linguistic factor and social factor contributes to the salient use of affix ‘er'.

Keyword：the affix ‘er';rhythmic meaning;rhythm-marked function;language contact;