An OH-type macroporous strong-base resin was evaluated as a heterogeneous catalyst for the oxidation of aldehydes to the corresponding carboxylic acids by molecular oxygen. A wide range of aldehydes, such as aromatic, aliphatic and cyclohexyl aldehydes, were found to be oxidized to the goal acids with high yields in a short time. Neither metals, hazardous oxidants, nor cocatalysts were involved in the reaction system. Solvents, temperature and O₂ pressure may have a significant impact on the product distribution. These process parameters were tested to determine the optimal conditions for the oxidation of 3,5,5-trimethylhexanal. The yield of the goal 3,5,5-trimethylhexanoic acid reached 88.1% under 0.3 MPa of oxygen at 45 °C after a 40 minute reaction with acetonitrile as a solvent and the alkaline resin as the sole catalyst. Cycle tests of the catalyst showed that it was easy to separate and recycle the resin, indicating the good application prospects of the alkaline resin for the title reaction.