Altered anticipation processes are implicated across various clinical samples, but few studies focused on the posttraumatic stress disorder (PTSD). We measured contingent negative variation (CNV) in a choice reaction paradigm among 58 survivors of the Wenchuan earthquake, including 28 individuals who were diagnosed with PTSD and 30 without PTSD. Compared to the non-PTSD group, the PTSD group had significantly larger CNV amplitude. On the behavioral level, although the reaction times were comparable between groups, the PTSD group committed more errors than the non-PTSD group. Furthermore, the total PTSD symptom severity score as well as the re-experiencing symptom score were positively related to CNV amplitude. These results suggested that individuals with PTSD might be more alerted to and anticipate more to upcoming events in their environment, yet still have degraded performance in response to the stimulus.