Crystalline polyoxo-titanium clusters (PTCs), as a molecular model of TiO₂ nanomaterials, have attracted unprecedented attention due to their designable structure, tunable band gap, catalysis, and photochromic properties. A new trinuclear Ti₃-oxo cluster, [Ti₃(μ₂-O)(μ₃-O)(abz)₆(OⁱPr)₂]·CH₃CN·H₂O (Ti3), was synthesized by solvothermal method with a yield of 60% by using 4-aminobenzoic acid as ligand. Single-crystal X-ray diffraction shows that it has a [Ti₃(μ₂-O)(μ₃-O)(abz)₆(OⁱPr)₂] trinuclear cluster structure. Ti3 crystallizes in monoclinic space group P2₁/c with a = 11.091(1), b = 22.837(2), c = 22.754(1) Å, β = 90.580(6)°, V = 5763.0(6) ų, Z = 4, D_c = 1.345 g·cm^-3, F(000) = 2412, μ = 2.743 mm⁻¹, R = 0.0796, and wR = 0.2260 (I > 2σ(I)). Ti3 shows typical semiconductive behavior determined by temperature-dependent conductivity test. The chemiresistive humidity sensor fabricated by Ti3 showed good performance, including high response (four orders of magnitude current change from 0 to 100% RH) and fast response time (160 s) and recovery time (26 s).