A series of cross-linked polyurethane(PU) elastomer samples with various crosslink density were synthesized from polyether diol(PPG2000), 4,4’-diphenylmethane diisocyanate(MDI), 1,4-butanediol(BDO) , trimethylolpropane (TMP) and glycerin. The cross-linking density of the PU elastomers was calculated by Flory–Rehner equation. The degree of hydrogen bonding, the microstructure and the morphologies of these PU materials were characterized by means of FT-IR, DSC and DMA. The experimental results showed that the PU elastomers containing a small amount of crosslink agent ( TMP or glycerin ) may make tanδ to a very low value above the ambient temperature. The PU elastomer samples using glycerin as curing agent can make tanδ to a low value in a lower temperature compared with the ones using TMP as curing agent.