Infrared (IR) small target detection has played an essential role in civilian and military fields. Considering the unsatisfactory detection performance of existing methods, this paper proposes an IR small target detection method named OSP-IRTD, including a principal component analysis-derived orthogonal subspace projector for background suppression and target enhancement, and a designed information filter for residual interference removal. Comprehensive analysis on three IR sequences with four competitive methods demonstrates the superior target detectability (TD), background suppressibility (BS) and overall performance of OSP-IRTD.