Tipα (TNF-α-inducing protein) from Helicobacter pylori is identified as a new carcinogenic factor. Tipα induces high expression of TNF-α through NF-κB activation, thus promoting host inflammation and tumor progression. The homodimer of Tipα as its active form for functional performances is cross-linked by a pair of inter-molecular disulfide bridges (Cys25-Cys25 and Cys27 and Cys27). Tipα (25～192) was cloned into pET22b and expressed as soluble protein in E. coli strain BL21 (DE3). Recombinant active Tipα was first purified through Ni²⁺-chelating chromatography, and then further purified by cation-exchange chromatography and size-exclusion chromatography to get the pure homodimer protein. Native Tipα and SeMet Tipα were crystallized and optimized using hanging drop and microbatch methods, with diffraction to 2.2? and 2.6?, respectively. These crystals belonged to C2 space group with similar unit-cell parameters. The native protein crystal had unit-cell parameters a=127.01?, b=47.57?, c=96.5?, α=γ=90°, β=127.5°. An attempt to solve the three-dimensional structure of this protein by MAD method is under way.