Abstract: 【Objective】 The C3d gene of camel complement was cloned and its sequence characteristics were analyzed to provide a basis for the study of its adjuvant effect. 【Methods】 Total RNA was extracted from camel liver using Trizol reagent, and cDNA was obtained by reverse transcription.C3d pecific primers were designed to amplify the C3d sequence by PCR technology, and the vector pMD18-T was constructed.The recombinant plasmid was transferred into competent strain and identified by double enzyme digestion.Clustw, DNA Star and Swiss-model software were used to compare the homology of the constructed recombinant C3d gene sequences, establish the phylogenetic tree, and predict and analyze its secondary and tertiary structures. 【Results】 Specific primers were designed and the 909 bp camel complement C3d gene was obtained by PCR amplification.T vector was constructed and transferred into Escherichia coli and a positive clone was obtained.Clustw was used to compare the DNA sequencing results with the sequences of bovine, pig, rabbit and human.The results showed that the cloned Bactrian camel C3d sequence had more than 97% homology with the C3d gene of Camelidae, and the homology with the C3d gene of bovine, pig, rabbit and human was gradually remote (88%, 88%, 83% and 83%, respectively).The sequence of C3d protein was analyzed by Swiss-model software, and the secondary structure of C3d protein was mainly composed of α-helix and β-fold, and it had good immunogenicity and protein-binding activity. 【Conclusion】 The C3d gene of camel complement was cloned.Sequence analysis showed that the C3d gene was relatively conserved in evolution, which provided the experimental basis and technical reference for the adjuvant effect of the gene and the subsequent research.