Blue phase (BP) stability is dependent upon chemical structure as well as the physical properties of the chiral nematic liquid-crystal (LC) mixture. In this study, the dependence of blue phase temperature range on alkyl chain length was investigated in order to evaluate the relationship between blue phase stability and the molecular structures of four kinds of n-cyanobiphenyl (CB) homologue chiral nematic liquid-crystal mixtures composed of rod-like nematic LC. It was confirmed that blue phase temperature range was strongly dependent upon the length of the alkyl chain and the elastic constant in n-CB homologues chiral nematic LC mixtures.