Abstract: We studied the genetic variation， the relationship between wood fibers and the optimum cutting age of pulpwood stand using 29 halfsib families in primary seed orchard of Pinus massoniana. The results showed that：the properties of fibers has certain variations among and within the family. The variation of fiber length, fiber width, fiber length to width ratio, flexibility coefficient and wall thickness to lumen ratio of earlywood were all larger than those of latewood. The variance analysis showed that the average latewood fiber width, average latewood tracheid diameter, average latewood fiber length and the average fiber length of earlywood and latewood were significant different among families, family hereditary capacity was 0.38-0.51. Our research also showed that the mason pine age had significant correlations with fiber length, latewood lengthwidth ratio, fiber wall thickness, tracheid wall thickness to lumen ratio, flexibility coefficient and rigidity coefficient; the width of annual ring had significant correlations with fiber width, fiber length, fiber lengthwidth ratio, tracheid wall thickness to lumen ratio, tracheid wall thickness, rigidity coefficient and flexibility coefficient; the percent of latewood had significant correlations with fiber width, fiber length, fiber lengthwidth ratio, tracheid wall thickness, earlywood tracheid wall thickness to lumen ratio, earlywood rigidity coefficient and earlywood flexibility coefficient; thus, the annual ring width could be an indirect index for selection of fine paper pulp making family of mason pine. After the evaluation of growth, fiber content and the wood quality, family No.113 was chosen as the fine paper pulp making family.