Wood polymer composites (wpc) have been extracting used for building Products, Automotive, Packaging materials and another applications. Wpc is subject to fungal attack due to wood components. Early detection of wood decay is critical because decay fungi can cause mass loss and rapid structure failure. The objective of this study was to compare the effects of two fungi Trametes versicolorand Coniophora puteana on the mass loss of wood plastic composites. Specimens as four various treatments: contain 40,50,60,70 percent of wood flour in composition, were exposed to brown rot and white rot for 4, 8, 12, 16 week. After each of mentioned time Mass loss was measured and its amount increased for each of treatments. As seen, most amount of mass loss occurred on 16th week after contamination and in samples with 70% wood flour about two fungi .Results shown that contamination time and wood flour percent in composition have direct correlation with composites mass loss. Also at same treatments and contamination times white rot has more severe effects on mass loss factor than brown rot.