Abstract: The fixation mechanisms of the main water-borne preservatives in treated wood were reviewed. The fixation mechanism of copper-amine/ammonia based-wood preservative systems was ionic exchange reactions between the active ingredients in the preservative with the carboxyl groups and the hydroxyl groups in the wood lignin and hemicellulose. In the micro-copper wood preservative systems, the fixation mechanism is attributed to the stronger adhesive force between the higher molecular dispersing agent and cellulose. For the boron-based preservative system, the fixation mechanism is similar to the copper-based preservatives, but the borate could not be fixed in treated wood directly. Therefore the research of the active ingredient fixation in treated wood deals mainly about the following aspects: 1) improving the hydrophobic propertics of boron-based preservative-treated wood; 2) complexing with organic chemicals and generating stable compound fixed in treated wood.