A polysaccharide fraction (FMPS) was isolated from floral mushrooms cultivated in Huangshan Mountain, and the rheological properties of FMPS in aqueous solutions were investigated. The FMPS solution showed shear-thinning behavior at 25 °C. Dynamic viscoelastic tests revealed that G′ and G″ exhibited strong dependences on the concentration and temperature. The FMPS/water system exhibited sol and weak gel behavior with the change of concentration and temperature. The exponent n of G′ ∼ ωn and tan δ also exhibited strong dependences on the concentration and temperature. The gel point (cgel) of FMPS solution was 1.16 × 10−2 g/mL at 15 °C, and the Tgel of 1.4 × 10−2 g/mL FMPS solution was 20.6 °C. Dynamic frequency sweep measurements indicated that the FMPS gel system was stable in the selected range of frequency. The heating–cooling process proved that the sol–gel transition of FMPS in aqueous solutions was thermally reversible.