Cauliflower is one of the most important popular vegetables in China. Cauliflower (Brassica oleracea L. var. botrytis) produces glucosinolates, which are secondary metabolites that have anti-cancer properties. The choice of suitable reference genes (RGs) for gene expression studies has a significant effect on experimental outcomes. In this study, we selected 15 candidates as RGs and analyzed them under heat, cold, drought, and salt stresses and methyl jasmonate (MeJA) treatment. The precision of the real-time quantitative polymerase chain reaction data was assessed using four methods (geNorm, NormFinder, BestKeeper, and ΔCt). The results revealed that EF1-β and ACT7; ACT1, EF1-β, and TUB6; TUA2 and EF1-β; HIS and ACT7; and ACT7 and ACT3 were the most stable combinations of genes for heat stress, cold stress, drought stress, salt stress, and MeJA treatment, respectively. The expression stability of the RGs fluctuated under different experimental conditions. Choosing the optimal RG for the specific experiment is therefore essential. This work provides relevant information for further gene expression studies on cauliflower and other closely related species.