The invention discloses a multi-core processor and a fault injection method thereof, and relates to the field of computer processors. The fault injection method disclosed by the invention comprises the following steps: when a hardware fault needs to be injected into a certain processor core of a multi-core processor, appointing the processor core as an attacked core, and taking another certain processor core as an attacking core; when the attacking core detects that the attacked core runs to an appointed fault injection point, changing the processor core voltage of the attacked core into an attacking voltage, and injecting a hardware fault into the attacked core; and recovering the processor core voltage of the attacked core to the safety voltage after the attacking voltage lasts for a preset time. According to the fault injection method provided by the invention, on the basis of not changing other nuclear voltages, other cores except the attack core and the attacked core are not influenced, and hardware fault injection is realized, so that the purpose of loading an untrusted application program into a security environment is achieved.