Background Depression is a mental illness common in university studies as they have high academic stress and their life transition. However, depression is being stigmatized by university students; hence they showed lower intention to seek mental health services when they are suffering from depression. Research targeting the short online stigma reduction program is scarce. Therefore, a short online psychoeducation training about depression which is regarding the theory of planned behavior, was employed in the current study to reduce university stigma towards depression and increase help-seeking intention.Method There were totally 40 undergraduate students in the Education University of Hong Kong divided into two groups to complete a pre-test survey, intervention, and posttest measure regarding depression. Among them, half were divided into the experimental group to receive psychoeducation training in the intervention stage, while another half were divided into the control groups to do the unrelated training to test and compare the effectiveness of psychoeducation training. The hypotheses were tested using mixed measure ANOVA.Result The results of the repeated measure ANOVA on SPSS suggested that university students who participated in the short online psychoeducation training could help reduce their threatening illness perception towards depression and increase their intention of seeking mental health service for depressive symptoms. At the same time, it did not indicate such result for those who did not participate in psychoeducation training. However, both two groups did not show a significant reduction in stigmatizing attitudes towards depression or improvement of acceptance towards students with depression. Thus, there was a trend of progress on these two components in the experimental group.Conclusion The current study indicated that the theory of planned behavior could serve as an approach for reducing threatening illness perception towards depression and increasing