In a novel high-speed disperser, the dimension and flow characteristics of highly viscous liquid (syrup) filaments were investigated, in order to lay the foundation for further study of the mass transfer of polymer devolatilization in the highspeed disperser. Results showed that the mean syrup filament diameter decreased with the increase of rotational speed and radial distance. Meanwhile, the mean syrup filament radial velocity increased with increasing rotational speed, but the variation trend of the mean syrup filament radial velocity with increasing radial distance was divided into three stages: ascending, steady and descending stage. The mean syrup filament tangential velocity also increased with increasing rotational speed; nevertheless, it increased initially, but decreased rapidly afterwards as the radial distance increased. Based on the experimental data of syrup filament velocity, the syrup filament shape was successfully modeled to obtain the bending degree, length, and specific surface of unit volume of syrup filament. In the meanwhile, the mean residence time and the number of syrup filament at different rotational speeds in the entire cavity zone were calculated, then offering essential information to further realize high-efficiency polymer devolatilization in the current high-speed disperser.