Abstract: Cementing slurries formulated with seawater are generally used in cementing the wells penetrating high pressure saltwater zones, long salt/gypsum formations, or wells drilled offshore. Friction reducers commonly used are difficult to disperse in the seawater cementing slurries, and have short dispersion duration and strong retarding performance. A polycarboxylic acid friction reducer with comb-like molecular structure has recently been developed to overcome these problems. The friction reducer was synthesized through free-radical polymerization, and was studied for its molecular structure and thermal stability using IR, SEM and thermogravimetric analysis. The effects of the friction reducer on the rheology, thickening performance and strength of cement slurries were measured in accordance with relevant industrial standards. The adaptability of the friction reducer to cement slurry was also studied. Thermogravimetric analysis showed that the friction reducer was stable at temperatures as high as 233℃. SEM and atomic force microscope measurement demonstrated that the friction reducer had comb-like molecular structure. This friction reducer was highly dispersible in cement slurries formulated with saturated saltwater or seawater, and had weak retarding power. It didn't deteriorate the strength of the cement slurries which were formulated directly from seawater.A cement slurry treated with the friction reducer had density of 2.72 g/cm³, filter loss of 24 mL, 24 h strength of 22 MPa, and good stability and rheology at 90℃. Good dispersity in saturated saltwater and good adaptability to high density cement slurry indicated that the comb-like polycarboxylic acid friction reducer was of high efficiency.