This study investigated the concreteness effect on both L1 and L2 mental lexicon organizations by comparing their word association responses respectively. The definition of “concreteness” of different classes of words was first proposed from the two perspectives of “the conception of space” and “ the experience of senses” by Langacker ( 2004) . The results indicate that concreteness effect does not change the nature of semantically-related L1 mental lexicon, however ; it does show some impact on the L2 mental lexicon, in which concrete words elicit far more semantically-related responses whereas abstract counterparts elicit far fewer syntagmatically-related ones. The rapidly expanded paradigmatic knowledge and fairly stabilized syntagmatic knowledge of concrete and abstract words in L2 mental lexicon provide strong evidence for the conclusion of the asymmetrical and asynchronous development of L2 semantic, syntagmatic-paradigmatic knowledge due to the concreteness effect.