There is an urgent need to identify biomarkers of the motor preparation process in cognitive neuroscience. In this study, voluntary and instructed action experimental paradigms were designed and 29 participants were recruited. The EEG microstate analysis method was used to calculate occurrence, duration, coverage, and transition probabilities of microstates for resting state, voluntary, and instructed conditions, as well as left hand (LH) and right hand (RH) movement conditions. We found significantly higher occurrence and coverage of microstate A in the motor preparation stage of instructed and voluntary conditions compared to the resting state. However, the occurrence, duration, and coverage of microstates between instructed and voluntary conditions did not show significant difference. Furthermore, the occurrence, duration, and coverage of microstate A were significantly higher for the left hand compared to the right hand. In addition, the occurrence, duration, and coverage of microstate B were significantly higher for the right hand compared to the left hand. Our results demonstrated alterations in the parameters of EEG microstates between the resting state and motor preparation. We also observed significant differences between left- and right-hand movements. These findings could help us understand the neural mechanism of motor preparation based on the whole-brain network.