Abstract: Natural decay resistance of 161 Chinese timber species (136 hardwood species and 25 softwood species) against white rot fungus, Polyporus versicolor Fr. and brown rot fungus, Lenzites trabea Pers. ex Fr., was determined by sand-block method in laboratory. The classes of their natural decay resistance can be arranged as follows:Cryptmaeria fortunei, Cupressus funebris, Fokienia hodginsii, Larix gmelinii, Castanopsis hystrix, Cyclobalanopsis chungii, Homalium hainanenses, Madhuca haiannensis, Quercus chenii, etc. are designated as class of very durable.Ketelecria fortunei, Pinus yunnanensis, Tsuga dumosa, Albizzia julibrissin, Juglans mandshurica, Querous nongnolica, etc. are classi-fied as durable class.Picea koraiensis, Ailanthus altissima, Albizsia falcata, Betula alnoides, Camptotheca acuminata, Casuarina equisetifolia, etc. are classified as moderately durable class.Picea jezoensis, Alniphyllum fortunei, Castanopsis carlesii, Liquidambar formosana, Populus davidiana, etc. are classified as perishable class.From the results obtained here, the specimens weight losses caused by brown rot fungus (Lonsites trabea) appeared lower than those by White rot fungus (Polyporus versicolor).