Anxiety (e.g., Dallos, 1976, 2006; Krashen, 2003, 2016) sometimes might be unavoidable in the learning process, because the cognitive and intellectual systems are usually connected with emotional factors. This empirical study was conducted in an English majors' advanced-level writing course to explore relevant explanations about why Taiwanese university students experienced "anxiety" (Tomlinson, 1981, 2016). Seventeen participants of junior grade at a southern Taiwan university had cooperated with their teacher to examine their anxiety occurring during writing in English. The findings discovered five key issues explaining their apprehension including mentioned (1) time restriction, (2) teacher evaluation, (3) peer competition, (4) uninteresting writing topics. The fifth factor repeated by most of the student is displayed by this study. The study implies the anxiety should be a negative impact upon language learning.