The effects of polyacrylamide (PAM) and polyvinyl alcohol (PVA) on morphology and structure of calcium silicate hydrate with C/S 1.0-1.7 prepared via precipitation in solution were investigated by XRD, FT-IR and TEM techniques. The results show that incorporation of the polymers decreased the order degree, increased the interlayer spacing and disturbed the layered stacking of C-S-H. Interlayer spacing expansion depended on C/S ratios and type of polymer. Interlayer spacing expansion had a minimum at C/S 1.0 and a maximum at C/S 1.3 and 1.5. Interlayer spacing expansion of PAM was bigger than that of PVA with the same C/S. C-S-H added with PVA mainly exhibited foil-like and fibrillar morphology. The fibrils were of variable length from a few tens of nanometers to a few hundreds of nanometers. Fibrils or foils seemed to be longer in the presence of PVA.