A self-incompatible (SI) line, S-1300, and its maintainer 97-wen135, a self-compatible (SC) line, were used to study the inheritance of maintenance for self-incompatibility in B. napus. The ratio of SI plants to SC plants from S-1300 9 97-wen135 F 2 and (S-1300 9 97-wen135) 9 97-wen135 was 346:260 and 249:232, fitting the expected ratio of 9:7 and 1:1, respectively. Based on these observations, here we propose a genetic model in which two independent loci, S locus and S suppressor locus (sp), are predicted to control the inheritance of maintenance for selfincompatibility in B. napus. The genotypes of S-1300 and 97-wen135 are S 1300 S 1300 sp 1300 sp 1300 and S 135 S 135 sp 135 sp 135 , respectively. S 135 is dominant to S 1300 , but coexistence of sp 1300 and sp 135 fails to suppress S locus. Both S 1300 and S 135 can be suppressed by sp 135 , while sp 1300 can suppress S 135 but not S 1300 . The model contains two characteristics: that a dominant S locus exists in self-compatible B. napus, and that co-suppression will occur when sp loci are heterozygous. The model has been validated by the segregation of S phenotypes in the (S-1300 9 97-wen135) 9 S-1300, the progenies of SC S-1300 9 97-wen135 F 2 plants and DH population developed from S-1300 9 97-wen135 F 1 . This is the first study to report co-suppression of S suppressor loci in B. napus. The genetic model will be very useful for developing molecular markers linked to maintenance for selfincompatibility and for dissecting the mechanism of SI/SC in B. napus.