Abstract:Using six inbred line cauliflower (Brassica oleracea Linn.var.botrytis Linn.) varieties from the Yangtze River basin as parents, general combining ability (GCA), specific combining ability (SCA) and correlation of primary characters such as head height, head diameter, head weight, maturity traits, bracts ratio and leaf coverage ratio were studied by 6 ×6 complete diallel cross and Griffing method I. Results showed that six characters were affected by additive and non additive effects. Maturity, bracts ratio, head height and leaf coverage ratio significantly affected by additive gene were mainly inherited by GCA; head diameter and head weight were mainly inherited by SCA and were strongly controlled by non-additive genes. Narrow heritability ranked in the order of maturity, bracts rate, leaf coverage ratio, head height, ball diameter and head weight. Concurrent selection of couple traits were head height and head weight, head diameter and head weight, head height and maturity, head weight and leaf coverage ratio, maturity and leaves coverage ratio; but independent selection of couple traits were head height and bracts ratio, head height and leaf coverage ratio, head diameter and maturity, head diameter and bracts ratio, head weight and bracts ratio, maturity and bracts ratio, bracts ratio and leaf coverage ratio. None interacted, and more traits of good characters were combined in the same cultivar. In the six inbred lines, P2 and P5 were ideal parental lines, and P4 was an ideal parental line for cold tolerance. The traits of P2×P4 in combination had better expression and SCA.