The flowing state of liquid medium for the rotor at high-speed rotation in a suspended rotor gyroscope was explored. The Reynolds stress model of hydromechanics was adopted to simulate the closed flow field between the rotor and the stator, and the Micro Particle Image Velocimetry (Micro PIV) technology was used to observe the motion of flow field and to measure the speed of flowing field. The simulation results indicate that the upper and lower surfaces of the rotor form different types of secondary flows with sidewall surfaces, and this phenomenon is enhanced with the increase of velocity and spatial dimensions. When the speed of the rotor increases to 7 500 r/min, the speed of secondary flow reaches 0.3 m/s, which means that reducing space dimensions helps to improve the motion stability of the rotor. The experiment proves that Micro PIV technology is capable of accurate observation of the flow velocity with the rotor speed at 0-1 000 r/min, and can meet the requirements of non-contact test of the flow field.