As the new era sees rapid development of internet technology and human society, idioms undertake constant modification and evolution, and see multitudinous variations created by language users. Based on a self-built corpus of Chinese and English data, this paper puts forward that both metaphor and metonymy are important motivations for the emergent meaning of idiomatic variants, and important components of the construal mechanism of the variant constructions. We find that metaphor and metonymy tend to form an orderly continuum, the boundary of which is definitely not distinct and explicit. We observe that in this linguistic phenomenon, the difference between Chinese and English lies in the types of interaction of metaphor and metonymy. Type I interaction, i.e. metaphor from metonymy is much observed in Chinese idiomatic variants, while beside type I interaction, type II, i.e. metonymy within metaphor can also be observed in English data. Furthermore, in metaphor-metonymy continuum for Chinese data, metonymy appears more in source domain, while in English data, it is also observed in target domain.