Rosin was used as raw material to prepare a rosin amide derivative. First, rosin was modified by acrylic acid with the weight ratio of 4.5:1. Then the modified rosin was reacted with diethyltriamine and the rosin amide derivative was produced under the following conditions: modified rosin and diethyltriamine mole ratio of 1:3.5, dimethylbenzene as water carrying agent, reaction temperature of 160-180 °C, and reaction time of 8h. The chemical structure of the product as a rosin amide derivative was identified by Fourier transform infrared spectroscopy, electrospray ionization-mass spectrometry, and 1H nuclear magnetic resonance analysis. The anti-fungal activity of the derivative was determined in vitro with wood decay fungi such as Aspergillus niger, Paecilomyces variotii, Trametes versicolor and Gloeophyllum trabeum. The anti-fungal experiment results signified that the derivative is active vs. these fungi, but less effective with Aspergillus niger. Since it is produced easily from rosin, which is renewable and not expensive, this rosin amide could be a potential wood preservative.