This study investigated the effect of cooperative learning on writing anxiety alleviation through a pre-test/post-test assessment. 120 EFL learners from a Chinese polytechnic institute were assigned into two groups: one experimental (cooperative writing) and the other comparison (solitary writing). Results revealed that cooperative learning facilitated mutual assistance among group members,received wide welcome from learners at different levels, reduced their foreign language writing anxiety and increased their writing competence greatly. Interviews were also carried out to probe further how cooperative learning helped to improve learners' psychological health and increase their participation in the writing class. The results are discussed in light of Social Interdependence Theory, relative research on writing anxiety and cooperative learning together with certain local elements. Suggestions are made on how to strengthen group cooperation and increase the effectiveness and efficiency of cooperative learning.