The thiomannoside is a key intermediate in the synthesis of polymannosaccharide. But its crystallographic study has not been reported. X-ray crystal structure analysis shows that the crystal of phenyl 2,3,4,6-tetra-O-acetyl-1-thio-α-d-mannopyranoside is in orthorhombic system, has P2 1 2 1 2 1 space group. Its unit cell dimensions are a=9.1731(11), b=11.574(2), and c=21.199(3)Å, α=β=γ=90.00°, Z=4, V=2250.6(6)Å 3 , D c =1.300g/cm 3 . The crystallographic study reveals that the thiomannoside is an α-anomer. Most interestingly, the structure provides an evidence of existing C–H⋯O and C–H⋯S intramolecular and intermolecular hydrogen bonds.