Low-resilience flexible polyurethane foams (FPUFs) with varying crosslinking densities, were synthesized from polyols, 4, 4-diphenyl methane diisocyanate (MDI-100), and water. The effects of crosslinking agent content, the molecular weight (M-w) of polyether diol, and the ratio of (polyether triol)/(polyether diol) on the resilience performance of FPUFs were investigated. Results indicate that higher crosslinking density was beneficial to the increasing of recovery time. The recovery time of the FPUF using polyether diol with M-w of 400 was 24.3 s. It was 3.2 times longer compared with FPUF using polyether diol with M-w of 3000. Dynamic mechanical analysis (DMA) results showed that, FPUFs with high crosslinking density displayed viscoelasticity in a wider range of temperature. However, when molecular chains were longer enough, FPUFs with low crosslinking density also demonstrated significant viscoelasticity, which is owing to the excess of physical crosslinking points. The results in stress-strain cycling and recovery time experiments were consistent with the results of DMA. POLYM. ENG. SCI., 55:308-315, 2015. (c) 2014 Society of Plastics Engineers