The English article system is well-known for its difficulty in second language learning of English. Since Chinese is a language which does not have functional categories corresponding to English articles, it is not surprising that Chinese learners of English have more difficulty with the English article system. Robertson (2000) shows the variability/non-convergence in the use of the English article system by Chinese learners of English by conducting an experimental study, designed to elicit spontaneous speech filled with referential noun phrases. More specifically, the variability here refers to that an article is used in some cases, but omitted in the exactly same context in other cases. After ruling out the possibility that the optionality is caused by a lack of articles in their interlanguage knowledge representation, the author divides the optionality into two categories: one is of systematic pattern which could be accounted for by several general linguistic principles; the other is unsystematic variation explained by Missing Surface Inflection Hypothesis (MSIH). However, this hypothesis has its disadvantage and is quite old as well. Thus, we intend to replicate his study, and reinterpret the unsystematic variation in light of Interface Hypothesis (IH), which is a more recent framework to account for optionality found in the interlanguage grammar of advanced and near-native L2 learners.