The invention provides an AC-DC system, a decoupling method thereof and protection equipment. The decoupling method comprises the steps of acquiring an AC voltage of an AC side of a converter; acquiring a fundamental component of a three-phase voltage and a DC component of the three-phase voltage; and performing voltage protection of the AC-DC system according to a relation among a fundamental wave effective value of the three-phase voltage, the DC component of the three-phase voltage and a corresponding protection action threshold. According to the decoupling method provided by the scheme, overvoltage protection is executed according to the fundamental wave component of the three-phase voltage acquired according to the AC voltage of the AC side of the converter and the DC component of thethree-phase voltage, voltage protection is executed by a positive DC voltage fundamental component, negative DC voltage fundamental component, positive DC voltage DC component and negative DC voltageDC component which are acquired according to a DC voltage of the DC side of the converter, so that strong coupling between AC-DC interconnection systems which are not connected by an isolation transformer is removed.