A method for performing host-directed operations is provided, where the method is applied to a controller of a Flash memory that includes a plurality of blocks. The method includes: in a test mode of the controller, when receiving a host command from a host device, extracting at least one portion of associated information of the host command, where the at least one portion of the associated information is an encoded result that is generated by performing encoding on a host-directed operation command; and analyzing the at least one portion of the associated information according to at least one predetermined rule, in order to perform a host-directed operation corresponding to the host-directed operation command. An associated memory device and a controller thereof are also provided.