【Abstract】 Object To compare the characteristics of the event-related potentials P300 between depression patients and long-term hospitalized schizophrenia patients. Methods 69 depression patients (DD), 69 long-term hospitalized schizophrenia patients(SD) and 70 healthy controls (HC) were recruited and P300 were detected. N1、P2、N2 and P3 components (Cz) were collected. Results Significant differences of P300 among three groups were found with both latencies (N1, P2, N2, P3) and amplitude (P3)(P<0.01). Compared with HC group, the SD group showed prolonged latencies (N1、P1、N2、P3) and decreased amplitude (P3) (P<0.01). Compared with HC group, the DD group showed prolonged latencies (N2、P3) and decreased amplitude (P3) (P<0.01). Compared with the DD group, the SD group showed prolonged latencies of N1,P1,N2 and P3 (P<0.01), except amplitude (P3) (P=0.787). Conclusion The chronic schizophrenia patients still have cognitive impairment and more than depressive patients. P300 may play a role of differentiating schizophrenia from depression.