Retinoid X receptor (RXR) belongs to the family of nuclear receptors activated by ligands. In this study, the cDNA sequence of the Sepiella japonica RXR gene was cloned using RT-qPCR; bioinformatics analysis was conducted on the sequence of nucleotide and protein structure in the CDS region of the RXR gene. The results showed that the CDS-domain nucleotide sequence of SjRXR was 1239 bp, encoding a protein composed of 412 amino acids. Moreover, the sequence analysis showed that the CDS region of the S. japonica RXR gene did not contain a signal peptide, possibly indicating that the RXR encoding protein was a non-secretory protein. There is no transmembrane structure in the protein structure, making it a non-transmembrane protein. Hydrophobicity analysis shows that the protein is more hydrophilic than hydrophobic. It also contains a domain of the HOLl family. The phylogenetic tree was constructed using the MEGA6 software employing the ML method. S. japonica is closely related to Octopus bimaculatus, which belongs to the phylum Cephalopoda, gathered into one branch. Thus the molecular evolutionary status of the RXR gene of S. japonica is consistent with its biological classification status. RT-qPCR was also used to analyze the expression characteristics of this gene in eleven tissues of S. japonica during four growth periods. The sjRXR gene was expressed in all tissues, and it was highly expressed in the liver, pancreas, brain, visual lobe, and visual gland. The sjRXR expression changed significantly during the four growth stages, increased in the liver, pancreas, brain, optic lobe, and optic gland, but was followed by a decreasing trend in the brain, optic lobe, and optic gland. These results speculate that SjRXR regulates S. japonica neurodevelopment, reproduction, and aging as an essential factor and provide a vital reference base for in-depth study of the RXR gene in cephalopods.