Abstract: The dynamic viscoelastic properties of fastgrowing poplar samples with difference initial moisture content were studied by DMA at the following conidition of temperature range from 35 ℃ to 350 ℃, heating rate with 5 ℃/min, measuring frequency with 1,10,50 Hz. The storage modulus results showed that the sample with 0 % moisture content got maximum elasticity at 95 ℃. With increasing temperature, the elasticity of samples with 12 %,18 %,30 % moisture content decreased slowly before 75 ℃,and decreased rapidly between 75 ℃and 130 ℃, for the sample with 12 % moisture content(equilibrium moisture content), the elasticity decreasing range was the smallest in all water content samples; For the samples with 50 %,80 %,100 % and watersaturated, the elasticity variety points happened after 135 ℃, the temperatures of elasticity variation points got increased with increasing moisture content，and had minimums elasticity at variation points. The loss modulus results showed that the glass transition never happened in the whole temperature range with 0 % moisture content sample; in all water content samples, 12 % moisture content specimens had the lowest initial loss modulus and secondary transition loss modulus, compared with the samples of 18 % and 30 % moisture content, the sample with 12 % moisture content had the highest temperature of secondary transition; the sample with 30 % moisture content (fiber saturation point) had the maximum viscosity in all water content samples. The data of loss factor also showed all the samples with water content had the process of glass transition, and the sample with 30 % moisture content got the lowest temperature when the glass transition happened. The measuring frequency with1, 10 and 50 Hz less affected on the storage modulus, loss modulus and loss factor, with the measuring frequency increased, the described curve of mechanical relaxation process moved slightly to high temperature.