The invention discloses a rectification design of a metal phase brush, which uses a synchronous relationship between a synchronous motor rotor and an alternative-current source phase to manufacture a metal phase brush serving as a synchronous switch to realize alternative-current rectification. An anode output block of the phase brush is always connected to a power supply block when a phase current is at an anode and a cathode output block is always connected to the power supply block when the phase current is at a cathode. Because a metal switch does not have unidirectional conductivity of a crystal diode, current feedback is caused when a voltage of a direct-current end of a capacitance filter is higher than an alternative-current phase voltage. According to the work voltage of the direct-current end, a conducting phase is calculated. When in single-phase full wave rectification, the direct-current voltage is an average voltage of a single-phase alternative current, and the conducting phase of 45 to 135 degrees and the conducting phase of 225 to 315 degrees are synchronous. When in three-phase full wave rectification, the direct-current voltage is 1.663 times the single-phase peak voltage, and conducting phases are of 43.5 to 136.5 degrees and 223.5 to 316.5 degrees respectively. The rectification design of the metal phase brush is characterized by breaking through the limitation of high voltage and high power and is suitable for electrochemical industry and high-voltage direct-current transmission. The voltage resistance between two electrodes of the phase brush determines the high-voltage rectification upper limit to which the phase brush can be applied.