This paper examines the theory of conceptual blending from cognitive linguistics to reveal the process of semantic change and the cognitive mechanisms in polysemous words. In this study, quantitative and qualitative methods are combined to explore the lexical semantic evolution trends of these two words, based on linguistic evidence from corpora. It is revealed that 闭bì and 蔽bì demonstrate a dynamic process of fusion and divergence in the semantic construction through conceptual blending. In their semantic evolution, there is a phenomenon of semantic alternation, where complementing the contraction of the ‘to conceal’ meaning in 闭bì is the development of the ‘to hide’ meaning in 蔽bì. The pattern of sense distribution for these two words had primarily formed in the Modern Chinese period, yet instances of mixed usage still exist in some regions.