This study investigated L1 Chinese learners' English article substitutions and analyzed possible causes. The participants were 60 Chinese speakers divided into an intermediate and an advanced group, 30 participants each. The instruments were a Fill-in-the-Blank Test, a Grammaticality Judgment Task, and an interview. The instruments were conducted based on the nominal contexts in the English article system, i.e., the [+def, +spec] context, the [-def, +spec] context, and the [-def, -spec] context (Ionin et al., 2004). Results from the tasks showed that both groups had problems of English article substitutions. Both L1 transfer and L2 related factors, i.e., complexity of English articles and false concepts hypothesized played important roles in L1 Chinese learners' English article substitutions. The results contributed to second language acquisition and provided some pedagogical implications.