This study aims to examine the causative factors which lead to non-parallelism in the derivation process of disyllabic words with the same basic meaning in modern Chinese by comparing the morpheme meanings and the word formations. It is revealed that although lexical derivation occurs in the hierarchy of words, it is still mainly restricted by morphemes, especially the meanings of morphemes. Besides, relations between words, pragmatic contexts and foreign languages influence the derivation as well. Chronologically, synonymous derivative meanings are in a long-term transformation from parallel to non-parallel, which shows the tendency of lexicon evolution.