Abstract: Specimens of tilia, populus and bamboo were treated with three water borne preservatives (CCA, FBBCr, ACB) against Polystictus versicolor, and an experiment on their toxicity against P. versicolor has been made. The differences of weight loss of specimens show the different effectiveness of the toxicity dose agents against the species of fungus. The correlation between the weight loss index of the specimen (Y) and the amount of dose agent absorbed by the specimen (X) can be expressed by regression equations. Take the CCA dose agent as an example, the linear regression equationfor tilia is: YT= - 2-75X + 37.77;for populus is: YP = - 3-04X + 35.03;for bamboo is: YB= - 1.44X + 24.95.The lethal dose (LD) of CCA for tilia is 11.9 kg/m3, for populus is 11 kg/m3, for bamboo is 17.3 kg/m3; the LD of FBBCr for tilia is 3.2 kg/m3, for populus is 4-6 kg/m3, for bamboo is 5.4 kg/m3; and the LD of ACB for tilia, populus and bamboo are 23.9 kg/m3, 20.9 kg/m3 and 32.5 kg/m3 respectively.