Abstract: The study focused on wood products made primarily from eucalyptus, including fiberboard, stand board, and plywood, with Pinus massoniana wood serving as the control. A brown-rot fungi (Gloeophyllum trabeum) was used to conduct a 180-day indoor decay experiment on the wood products. Specimens were sampled at different intervals (every 60 days), and the organic carbon content and chemical component levels were measured using the wet combustion method. A univariate linear regression model was employed to estimate the time required for complete carbon emission from the wood products, aiming to explore the carbon content variation mechanisms and brown-rot degradation processes in eucalyptus products.The results showed that the mass loss rate of the boards increased with prolonged decay time. The carbon content of fiberboard decreased, while the absolute carbon content of stand board, plywood, and Pinus massoniana initially rose slightly before declining.The biological degradation of brown-rot has a significant impact on the carbon content of wooden products,selectively degrading cellulose and hemicellulose, but have limited degradation of lignin.The relative increase in lignin proportion was the core factor driving the rise in absolute carbon content. The carbon emission cycles for brown-rot degradation in fiberboard, stand board, and Pinus massoniana were 625, 321, and 387 days, respectively.