Vortex optical trap is generated by projecting computer-generated phase patterns to liquid crystal spatial light modulator. Because vortex beam itself owns orbital angular momentum, it can be utilized to trap and rotate yeast cell. The angular rotation rate of yeast cell is measured by Fourier transforming of rotation time-sequencial signal. Besides, how laser power, topological charge and height of the vortex trap from bottom affect the angular rate of rotation is discussed in detail. The experimental results indicate that the rotation rate is proportional to laser power, but inversely proportional to the square of the topological charge. The rotation rate reaches maximum when the height of trap is about 14 μm. The sign of topological charge determines the direction of rotation of yeast cell. When the sign of topological charge is positive, the yeast cell rotates counter-clockwise, and it rotates clockwise when the sign is negative. The results may find their potential applications in the measurement of the torque of bacterial flagella motor.