The full-length Mag 29 gene of Dermatophagoides farinae was amplified by RT-PCR with a pair of specific primers. The PCR product was cloned into pCold TF DNA vector. The constructed plasmid pCold TF-Mag 29 was transformed into E. coli BL21 and followed by expression of the protein induced by IPTG. The recombinant protein was analyzed by SDS-PAGE. The full-length Mag 29 gene was 429 bp. A specific band (Mr 63,000) were detected in the whole cells, the supernatant, and the precipitate. Bioinformatics analysis revealed that Mag 29 protein was composed with 142 amino acid residues with a calculated molecular weight of Mr 15,100, and its secondary structure was composed of alpha helix (55.63%), extended strand (3.52%), and random coil (40.85%). The Mag 29 allergen was a hydrophilic and cytoplasmic protein, and shared a high degree homology with the heat shock protein 70 family.