A multi-chip package, a controlling method of the multi-chip package and a security chip are provided. The multi-chip package includes a memory chip and a security chip. The security chip is coupled between the memory chip and a host. The security chip includes a processing circuit. The processing circuit is for enabling a security path to input an input-output signal into the processing circuit for executing a security procedure and accessing the memory chip, if a command is received by the processing circuit and the command includes a security requirement.