Compared with the study of acquisition of syntax and morphology, there is a relative lack of research on the acquisition of phonology, the L2 acquisition of word stress in particular. This paper investigates the production of word stress by 70 Chinese college students in their reading aloud. Altogether 350 minutes' recordings were collected and coded. The result shows that improper assignment of word stress most likely occurs in two-syllable words and three-syllable words and on the first syllable. The factors which account for these problems are learners' insensitivity to syllabic structure of English words and lack of knowledge of rules on English word stress.