The invention discloses a fullerene liquid crystal compound which has a high refractive index and contains double-bond functional groups, a preparation method of the liquid crystal compound, and an application of the liquid crystal compound serving as a filling material in the field of photonic crystals. The fullerene liquid crystal molecular structure is composed of three parts, namely a rigid fullerene acid part, a flexible double bond-containing gallic acid derivative part, and a flexible chain segment part connecting the rigid fullerene acid part and the flexible double-bond-containing gallic acid derivative part; the precursor of the flexible chain segment is diol; and two ends of the flexible chain segment are respectively connected with the fullerene acid part and the double bond-containing gallic acid derivative part through ester bonds. The fullerene liquid crystal compound has high refractive index, so that the compound can well replace a liquid crystal molecule with low refractive index to serve as the filling material of the photonic crystal, and the photonic crystal with high refractive index contrast ratio and excellent performance is obtained.