Objective To explore the effects of transcranial direct current stimulation（ tDCS） intervention on cognitive function in schizophrenic patients. Methods A total of 39 schizophrenic patients with cognitive impairment were randomly assigned into active tDCS group and sham tDCS group. All patients received daily active-tDCS or sham-tDCS on 10 consecutive work days as an adjunctive therapy to treatment as usual. The anode was placed over the left dorsolateral prefrontal cortex with the cathode over the right supraorbital ridge. The active tDCS was given continuously for 20 min at 2 mA. For the sham tDCS， the electric current lasted only 40 seconds though the electrodes remained in place for 20 min. The MATRICS Consensus Cognitive Battery （MCCB）， the Paced Auditory Serial Addition Task（ PASAT）， the CogState Battery， and the Reading the Mind In the Eyes Test（ RMET） were administered at baseline and four weeks after the last session to evaluate the changes in cognitive functions. Results The patients in the active tDCS group showed a non-significant superiority over those in the sham tDCS group in most of the cognitive domains at the four-week follow-up. Nevertheless， only processing speed yielded a trend preferring the active tDCS group（ F=4.087， P=0.051）. In the active tDCS group， a better global cognitive function at baseline predicted a higher MCCB composite score at the follow-up （Z=0.085，P=0.011）. Conclusions There remained some cognitive modulation effects four weeks after the end of 10 sessions of tDCS. However， larger sample studies are on demand to confirm our findings.