Objective To explore the relationship between childhood trauma and suicidal risk in prisoners and the mediating effect of alexithymia in this relationship. Method We investigated a total of 362 male prisoners in Guangdong Province using Childhood Trauma Questionnaire-Short Form (CTQ-SF), the Twenty-item Toronto Alexithymia Scale (TAS-20) and Suicidal Behaviors-Revised Questionnaire (SBQ-R). Results Thirty-five (9.7%) prisoners had a high risk of suicide. The total score and the dimension scores of the CTQ-SF was positively correlated with the total score of SBQ-R (r=0.065-0.358, P<0.01) and the total score of TAS-20 (except for the dimension score of sexual abuse) (r=0.156-0.255, P<0.01). The total score of TAS-20, the dimensions scores for difficulty in identifying and describing feeling and the dimension score for externally oriented thinking were positively correlated with the total score of SBQ-R (r=0.330, P<0.01; r=0.294-0.305, P<0.01; and r=0.130, P<0.05, respectively). The results of structural equation analysis showed that alexithymia had a partial mediating effect on childhood trauma and suicide risks (β=0.07, 95%CI: 0.023-0.121, P<0.05). Conclusion Childhood trauma affects suicidal risk in prisoners not only directly but also indirectly through the mediating effect of alexithymia.