Online learning brings EFL students the new experience of writing instruction. On the one hand, the new experience in online learning may lead to excitement; on the other hand, it may also result in problems such as anxiety. The current study aims at tracing the students' writing anxiety levels, identified the causes of anxiety problems, and put forward strategies of solutions. The results of the data analyses show that out of 149 students involved in this study, 115 students had a high level of writing anxiety and the other 35 students were of medium and low levels of anxiety. The results of the study also indicated that anxiety problems were predominantly caused by time constraints (3.92), linguistic factors (3.70), and feeling afraid of negative evaluation from peers and the teacher (3.63). Furthermore, students also reported conditions that made their writing skills stagnant, for instance, limited writing practice (3.57), insufficient writing technique (3.57), and shortage of feedback (2.81). The qualitative data revealed that numerous strategies implemented by highly anxious students to reduce their writing anxiety in online writing instruction include doing more linguistics activities, doing self-anxiety treatment, implementing writing techniques, building resources, and increasing their self-confidence. Understanding the numerous causes of anxiety, further research may investigate teachers' strategies to help students reduce their anxiety.