Ⅱ-32A, an elite male-sterile line of rice (Oryza sativa L.), has been widely used for the production of hybrid rice seed in China. Heading date in most combinations using Ⅱ-32A shows transgressive inheritance or similarity to the latter parent, but the genotype of Ⅱ-32A with respect to major genes for heading time is unknown. This limits the further exploitation of this sterile line in breeding and hybrid seed production. Using a number of major gene heading date isogenic lines and heading date QTL near-isogenic lines, we genetically analyzed Ⅱ-32B under both long- and short-day conditions. We show that Ⅱ-32B carries two photoperiod-sensitive genes, E1 and E3, a recessive late-heading gene, ef-1, and a photoperiod-sensitive allele, Se-1u. In addition we identified in Ⅱ-32B a recessive inhibitor for E1 or Se-1n and other modified photoperiod-sensitive genes. The heading-date constitution of Ⅱ-32A was determined to be E1e2E3Se-1Uef-1i-Se-1.