Abstract: The polymer-solvent interaction parameter μ for poly (cis-1, 4-butadiene) was determined by stress-strain measurements of swollen gum and black vulcanizates. It is found that μ is a function of vr, μ = μ0+ βvr. The μ0 valuethus obtained is consistent with those determined by osmometry and light-scattering. The effective network chain densities of vulcanizates with different degree of curing were calculated by Flory-Rehner equation. The influence of effective network chain density for poly (cis-1, 4-butadiene) on vulca-nizate properties, such as tensile stress at 300% elongation, tensile strength, tear strength, ultimate elongation and so on were studied.