Objective To investigate the complementary feeding status of Beijing 4~12 month-old infant, and to provide a scientific basis for the infant nutrition intervention. Method Stratified cluster sampling method was used to extracted 4~12 months infants in Beijing suburb and urban, collected the information of infant food supplement to make statistical analysis through questionnaires, and calculated the complementary feeding index of infants. Results There were 900 infants, urban 431, suburb 469.The index included DDS, FVS, the first time of food and milk.For aged 4~6-month and 7~9-month infants, dietary diversity score (DDS), food variety score (FVS) and complementary feeding index had significant differences between urban and suburban infants.For aged 10~12-month infants, DDS and complementary feeding index had significant differences between urban and suburb.For aged 4~6-month and 10~12-month infants, the factor associated with complementary feeding index was the cost of food.7~9-month infants, the factor associated with complementary feeding index were the costs of food and mother's culture. Conclusion The complementary feeding index can evaluate complementary feeding of infants comprehensively, and the validity of the index should be evaluated.