Objective To investigate couple's personality similarity effect on the marital quality, and to explore the vairance of such effect under different levels of spouse's depression. Methods The cross-sectional data of 4644 couple from the national survey of mental health database in china(2009) was used. Couples completed Locke -Wallance marital adjustment test, The CES-D scale a self-report depression scale and Eysenck personality questionnaire short scale for Chinese version (EPQ - RSC). Results The personality similarities of couples(0.44±0.27) and their marital quality (wife (103.71±27.54), husband (106.15±26.94))had significant positive correlation (r=0.25~0.27, P<0.01). Regression analysis showed the effect of personality similarity on the marital quality were varied according to the level of spouse depression(β=0.09-0.22, P<0.05). Among participants whose husband or wife had higher level of depression, couple's personality similarity had stronger effect on his/her perceived marital quality. Conclusion Husband and wife personality similarity is related to marital quality significantly, and the spouse depression plays a significant moderating role in this relationship. Key words: Personality similarity; Marital quality; Spouses' depression