Abstract:Hebei poplar is a type of Populus tornentosa Carr. Width of growth rings and fiber morphology were determined. The variations in fiber length related to tree type, growth rings and positions in stem from centre to circumference and base to top. Mean value of more 1.50mm fiber length was found in a type of Yi County, Hebei province in China. It is the maximum length here been recorded for poplar. Results showed that there is a regular increase in fiber length with age of tree. Fiber length increases rapidly at young stage, the maximum length is reached in about 12—14 year, afterwards becomes stable. The fiber length (y)-age (x) relation is expressed as y=1.0490+0.0377x-0.0006x2. It‘s favour the species as a valuable fiber source for some speciality pulpwood species and other fiber industry.