The invention discloses a motor control system, and a compensation method and a compensation device of direct current bus voltage of the motor control system. The motor control system comprises a rectifying circuit, an electrolytic capacitor, an inverter circuit and a voltage sampling circuit used for sampling the direct current bus voltage. The compensation method comprises the following steps of acquiring frequency of an alternating current input power supply; calculating a phase deviation generated during sampling of the voltage sampling circuit according to the frequency of the alternating current input power supply; and compensating the direct current bus voltage according to the phase deviation to control the inverter circuit according to the compensated direct current bus voltage. Therefore, an influence of a ripple wave on motor control can be eliminated by compensating the direct current bus voltage; precise control on a motor can be realized; and stepout outage of the motor can be effectively avoided.