Abstract: This paper aims to study the stress relaxation properties of thin wood composites based on the theory of cantileverbeam bending.According to the stress relaxation tests,we found that this detection method was feasible.From the stress graph and test data of stress relaxation properties,it was found that the attenuation extent of stress was fast at the beginning,but slow aftenwards. After 2 hours test,we can get an ideal stress relaxation.The test waves of the highdensity fiberboard and the particle board were smoother, the test stress of the medium density fiberboard was slightly worse. Besides, obvious ripple was found from the test stress curve of wood fiber plastic.The relaxation coefficient m can reflect the attenuation extent of stress directly,the bigger the value of m was,the more serious the stress decay was.