A high-speed rheometer includes a base, a driving device disposed on the base, a lower sample assembly connected with the driving device, an upper sample assembly disposed above the lower sample assembly, a torsion bar disposed on the upper sample assembly and being torsional upon the rotation of the upper sample assembly, and an optical torque measuring assembly. The lower sample assembly is rotatable under the driving of the driving device, and the upper sample assembly is rotatable under the driving of the fluid. The optical torque measuring assembly is used to measure a torsion angle of the torsion bar so as to obtain a torque generated during shearing the fluid to be tested.