Copper ions in Alkaline Copper Quaternary (ACQ) preservatives are easy to lose, which threaten the environment and human health. In this paper, the anti-loss and comprehensive performance of ACQ are improved through biological modification technology. Chitosan was used as the research object and the nano-chitosan solution was prepared by ion cross-linking method. ACQ anticorrosive wood was modified by nano-chitosan and the anti-loss and physical properties were investigated. The results show that when the mass ratio of chitosan solution to sodium tripolyphosphate is 5∶1, the diameter of nano-chitosan particles is 376 nm; the fixation rate of copper ions is increased from 87.89% to 95.35%. The residual rate of nano-chitosan modified ACQ anticorrosive wood at 600 ℃ is 22.03%, and the water contact angle is 69.5°. Meanwhile, the anti-loss, thermal stability and hydrophobic properties of nano-chitosan modified ACQ anticorrosive wood have been significantly improved.